Tamron Adaptall lens rear cap MKII

This is a minor tweak of the original design by John Beardon (thanks for doing the heavy lifting John!). It has thicker walls projecting up from the cap base (requiring a slightly reduced inner diameter) and wider, taller (but not thicker) bayonet lugs. These mods make the cap fit tighter on the lenses and minimize the chances of caps coming off in your camera bag if they get knocked around. The thicker inner wall seemed necessary to increase rigidity when printed in PETG, rather than PLA.