I think I've seen this done before when someone went to a regional and did a before and after on their thoughts, so I'm going to attempt to also.

I practiced yesterday on the pattern and was thrown for a loop for what line to play that gave me the most forgiveness.  I could get to the pocket from just about any line w/ the right ball and wrist position, but I couldn't find anywhere that gave me 1 board of forgiveness.  Outside of 10 is a complete oil fest and if you miss right in the track area, you just picked up the 10 pin.  You can play outside 10 but it has to be straight up the boards and perfect speed.  My initial thoughts are that I'm going to play 15 out to 11 with my stacked doom to start and see where that takes me.  I got the best carry from there, but again, if I miss right, then I'm shooting a spare with the head pin.  Not feeling to good about spares on the left side either.  I'm used to playing a little hook into 4's, 7's...and of course, it is and over under nightmare across.  I had the most luck throwing my 5x3 zr40 hard at those, so I'll cross my fingers there.  Here is my tournament arsenal.

Agent 4 x 4 . No weight hole
Doom 4 x 4.  No weight hole
44 magnum 5 x 4. No weight hole
ZR40  5 x 3 No weight hole
Spare ball--too much forward pitch, need to redrill thumb

As you can see, I don't have any pin down drillings and probably would have been helpful for this weekend.  I will post back Sunday night to update my standing.
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Shane Soule

It sounds like you fell into the trap alot of bowlers fall into at practice sessions. They throw for the whole practice session with a bunch of different balls. So they assume the shot will be exactly the same during the qualifying.
You can throw quite a few shots during a 2 hour practice session which will put some wear/tear on your body. Then you compound it during the 1st part of qualifying by adding on the mental fatigue. So by day 3 your body basically says" NO MORE!!!!!!".
When you try another regional.
Try to lengthen out the time between each shot.
Also move around from end to end of the house to see if the house plays the same.
Watch other bowlers with similar styles to see if their ball reaction is similar to yours.
Don't be afraid to ask questions during the practice session either.
This is the time and place to do it.
Its better to work on your equipment now than trying to do it during actual competition.  

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If it doesn't have DT or RG stamped on it.
Just leave it in the bag.

You have to keep your legs in shape to avoid tightness along with general stretching exercises.
Your putting your body thru quite a bit of stress in a 2 or 3 day span of time.
 From my own experience I liked the bowling but hated the driving to and from regionals. So I limited myself to 4 or 5 hr drives away from home. Also had a good roommate at the time which helped keep expenses down.
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If it doesn't have DT or RG stamped on it.
Just leave it in the bag.