Yes I have 3 different valve sizes and a stock of about 10 per size 38mm, 60mm and 80mm for myself.
If it were for a team I would certainly would not use extenders, as reliability would be a #1 concern for me as a team sponsor or leader I'd hate for someone to drop out of a race because I was to cheap to supply reliable tubes, extenders leak often and can be a pain to fill and deflate at times.
Give your team what's needed to win and the most reliable not cost effective to save a few bucks I'd be pissed if I were in a race and dropped out because of a $2 part!!! and for you most likely less.

To answer your original question yes 38's would most likely be the best extender don't forget the teflon tape that should go with it.