If I were a custom bowyer that offered custom grip options, I would offer (for an added cost) the materials needed and the instructions to do this IN ADDITION to any other charges for making a custom grip. Talk about a selling feature!!!
I cannot count the number of relatively new, high end bows that I have seen sold on Classifieds (I've bought a share of them
:p ), that one of the main reasons that the lister states they are selling is because of the grip.
Bows are like anything else, there are a plethora of good, custom makers out there, and, unfortunately, a purchaser tends to blame the bowyer if the grip doesn't suit them.
SOOO, I see two logical choices - no custom grips ( :( bad choice IMO), or, offer custom grip only if customer provides mold of grip that they like (again for additional costs associated).
Off my soap box now!!!