Some people overcomplicate things.  I have exactly two IT thumbs, both the same size, which is a size larger than normal, and I put two pieces of tape in.  If for some odd reason my thumb actually swells, which it doesn't and shouldn't, (provided you don't drink excessively during bowling, among other things unconnected to actual bowling that cause body swelling), I'll be able to remove the tape, but I've never had to.  The second slug is just a backup in the unlikely event my primary slug fails. 

Here is my method of installation for both systems: https://www.youtube.com/watch?v=JtI0vkbKD3s 

Since making these adjustments, primarily roughing up any surface being glued, I've had literally zero failures out of either system for anyone.  The plastic piece on the bottom of the slug used to come already glued to the slug, but it doesn't anymore.  I'm glad for that, because that used to be a common failure area.  Now that I'm able to sand the surfaces before gluing, they never come apart anymore.  The safety molly is also better now, because instead of just gluing it in there as a fail safe, it actually acts as another anchor for the piece on the bottom of the slug. 

Even if you don't drill a lot of balls, getting just a couple slugs worked out just right and being able to have the exact same fit in each ball is worth getting the system for.  My hand gets tacky occasionally too, but you can adjust hole texture and play with tape to alleviate that.  I also put a vent hole near the bottom of the slug in the vent slit on the side to prevent suction if your thumb fits too well. 

Drilling different sized or angled thumbs is ridiculous in my opinion.  I used to swell and shrink quite a bit, but as soon as I fixed my fit, I have no more issues.  The slug should also always be drilled at 0, trying to play with different thumb angles during bowling can only be problematic or aggravate an already existing problem.  I roll over my thumbhole when I throw the ball straight at spares, and I have no problems.  I'd say it has more to do with how it hits in the pit than rolling over it. 

I still suggest putting a regular slug in your spare ball, or at least have a dedicated IT slug that stays in your spare ball if you want the exact same feel.  That being said, there's no reason to have more than two slugs drilled exactly the same for either backup, or using a different ball on each lane, or if you have a dedicated one for your spare ball.  People who have 4 or 5 different slugs are putting a bandaid on a problem or needlessly complicating things. 

My fit is perfect, but my hand swells and shrinks, sometimes during a league night. All I drink is water, so it isn't anything to do with alcohol. Most of the time in the winter, I use my smallest thumb. In the summer, I swell up two sizes. In the spring and fall, I never know what size I will use. I have three sizes that I use based on weather.

Tape isn't a bandaid if it never comes out . . it's a way of creating a little space between your thumb and the hole to avoid suction on the release, or reducing the friction.  I used to buy 500 count rolls of white tape because I'd swell and shrink like crazy CONSTANTLY, and I'd go through one of them every year.  I'd have to put in 3-5 pieces when I got to league because everything was a crater, and inside of a game it would all come out.  Got down to Albuquerque for nationals when it was there, literally couldn't get my thumb into anything, holes all had to be drilled out, but as soon as we got down to bowl, I couldn't hang onto anything and had ran out of tape.  Since I fixed my fit and don't grip anymore, I still have over half the roll of tape left that I bought in 2008 after we got back from Albuquerque, and my wife has used most of that. 

If you want to spend $150 on slugs, I'm sure your pro shop won't argue with you, I just think it's completely needless, and that's coming from somebody who used to go through 500 count rolls of tape in one season.  I get the idea, I just know the cause and think it's fixable without drilling 5 or 6 different sized slugs. 

Who was that in response to . . ?  A few pieces of tape isn't a bandaid, agree with that.

I live in Kansas, where it was 35 degrees this morning and will be 75 today, gets to over 100 in the summer and below 10 in the winter, I eat just about anything I can get my hands on, usually have a couple drinks while I bowl, and just traveled to Springfield over the weekend to bowl.  League last Tues and Thurs, drove to Springfield Fri, bowled 6 games Sat, 3 games Sun all while completely gorging myself whenever we ate, then league again last night.  No tape went in, no tape came out, same slug. 

Like I said, before I changed my fit and stopped gripping, I went through 500 pieces a year.  The smallest thing in the world would make my thumb go nuts, but when your thumb is artificially enlarged due to bad fit, gripping, clutching, excess friction on release, etc., it's going to enhance or increase the influence of any outside cause for swelling or shrinking.  When I went to Albuquerque in 08, I just used slugs back then, when we got there to bowl, I had to have everything actually put on the press and drilled out because my thumb was so huge.  Hour later I couldn't hang onto anything and had to reslug everything when I got back home. 

Now I have one slug that I've used for several years, went to Reno and back no problems, Baton Rouge, Springfield a couple times, 2 pieces of tape always stay in the hole, just need replacing every couple months. 

I'm not saying no one should ever swell or shrink, I'm not saying everyone has a bad fit, I'm not saying everyone grips . . but if you actually have a need or use for 4 or 5 different slugs, you're doing something wrong and it would be in your best interest to check into it.  Coming from somebody who used to go through 500 pieces a year, and now only goes through maybe 20, and that's just to replace old worn out tape, it's not like I don't at least understand the problem or issue or haven't been there.  If you want to drill 4 or 5 slugs, that's up to you, but I wouldn't recommend it to people like it's the norm, because in every case where I've had requests from people to drill several different sized slugs, it's always because they have fit or gripping issues.  Not trying to be a dick or look down on people from my perch, I just feel very strongly that there's a better way, and seeing as how I used to be there several years ago, I'm very familiar with the situation. 

So tape is a bandaid if you have to add or remove a piece or two?

 You must live in a climate controlled environment, eat the same thing every day and don't travel much and bowl in different climates.

For the experts on these slugs.  Can one drill these interchanbable inserts at different pitches than 0, 0 to the pitch that was originally intended?

I think I saw some comments to that affect above..

Regards,

Luckylefty

Funny, I would think that guys like Norm Duke and Wes Malott would be able to find a competent driller who could give them a proper fit instead of fiddling with all that tape we see them using on TV. 

Normally the slug is drilled at zero and the pitch is in the ball.  You can alter the pitch when you drill a new IT but you have to be sure the drill will not go thru the sides of the slug.  Example, if you ball already has 1/8 reverse and 0 lateral and you want to try 0 reverse and 1/8 lateral, you would drill the slug 1/8 forward and 1/8 lateral.  This pitch will offset whats in the ball and the result is what you wanted.  Again, this is mostly for experiments.