I'm probably getting this system in my equipment soon enough. So I'm just wondering what you guys do when you need to use your spare/plastic ball to convert the spare. Do you wait for your strike ball to come back and switch the thumb out and in to your spare ball, or do you have another slug of the same size just for your spare ball?
My thumb shrinks while I bowl. My thumb is normally swollen to start with I guess, so if I want to keep the hole snug I have to insert 2-3 pieces of tape which I normally neglect. I will use a larger insert to start with, and switch to a smaller one when it starts feeling big, which is usually after about 8 shots.