The original 915 shifter is a work of art already, especially compared to a bug shifter or a 901 shifter. Look closely at one
in your hands and you'll understand why.
The sloppy shifting is caused by (partly worn) couplings and bushing further downstream the shifting action.
Funny thing is the original porsche coupling at the tranny nose-shiftrod has a build-in play!! This is done to accomodate the for-aft movement of the engine/tranny, preventing it from being pulled out of gear.
Makes sense, but not needed in a bug with good engine support.
There is an upgrade for the coupling bushing: get one and while your shopping at Pelicanparts, also try to get the factory short shift kit, which was available for the 3,2 cars. Fits all 915 shifters and work like a charm.
I have the above combo in my bug after I did the same research you did
Cheers,
Walter