Ok Opinion based question.

You are bowling a league, standard easy THS. You know you can tear them up if you use reactive gear, stand left throw right watch them fall, but you decide to use urethane for the challenge of it and what the hell something different instead of the usual. You carry a 205 with the urethane probably could have been higher if you used reactive.

You go to state the following season using your 205 average, but you bring modern gear and do well. Are you sandbagging cause you used urethane in league? Or smart, because you worked on accuarcy and spare shooting in league with the urethane ball, essentially using league time as a practice session.   

IMO you are smart, prepping for a difficult shot using means open to you. Didn't miss spares on purpose you tried every week using sub standard (compared to modern gear) equipment.

I have not done this just a random question. I do use urethane in a couples league averaged 217 with it last year. But I bowled other leagues with reactive gear.