I did that very thing last week.  Bowling at Sam's Town I left my particle ball (Track Money) in the trunk of the car, figuring I won't need THAT ball.  I put in a much milder ball.

As it so happened we had an unusual amount of carry-down that night and the Money would have been perfect, but alas, it wasn't available to me.  I could hit the pocket with all the balls I had, but hitting obviously isn't synonymous with striking.  In this case I almost ALWAYS go with the strongest ball.

Well, I put myself in this exact position tonight, by accident. I "only" had the 4 ball bag with me - but one slot had the spare ball, and one had the very weakest ball I own.
I was left with the Deuce and the Smash/R. I used the deuce for the first two games, tried the Smash/R with no success, went back to the deuce for the 4th game, bowled well. (We bowled a double set tonight, so...) Changed pairs, bowled OK with the deuce the 5th and 6th games. Lanes dried out a little, but there was WAAYYYY too much OB outside 5 for my liking - weak ball or strong. And terrible over/under from 5-12. So, I tried moving in deep with the deuce - TOO much ball. Sigh. Moved a little less deep with the Smash/R. Now - I WAS getting tired, but I believe I was seeing an over/under situation around 18 at the arrows out to 13. Bowled like crap the last two games. (156-166).
Sigh. Not all of it was the ball, but talk about an impossible matchup!
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I start each day with yoga and meditation. I put my right foot under my left thigh. I put my left foot under my right thigh. I arch my back as much as I can, and then I begin my mantra: Ouch, oh, that hurts.

Mike,
I tried everything. I softened the release, came up the back, hit up harder, etc..
It just wasn't my night.
Unfortunately, every night in this summer league isn't my night. I think I'm carrying right around a 185 this summer. Sigh.
It's gotta get better, or there are going to be a WHOLE LOT of bowling balls for sale real soon.
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I start each day with yoga and meditation. I put my right foot under my left thigh. I put my left foot under my right thigh. I arch my back as much as I can, and then I begin my mantra: Ouch, oh, that hurts.

I'm probably in the minority, but I'd opt for a stronger ball, and deal with it on a drier condition.  I can usually take some of the hand out of a stronger ball and tame it down several notches, but I have a very difficult time getting a weaker ball to work well on heavy oil conditions.  If nothing else, you can always take a stronger ball and throw it into the Lustre Kleen (as bad as I hate 'em), if the house happens to have one that is working.

I've gotten to where I primarily carry stronger equipment with me most places.  If I'm going to an unknown house, I might carry one medium ball along, just in case, but it has gotten to where my only medium equipment balls are some 10 years old now.  At least I would guess that you'd call a Trauma Response (scuffed 600 grit) and a Complete Chaos (scuffed 1000 grit) stronger balls.

Edited on 6/13/2003 1:51 AM