For the knob, i don't know.

Shortening the knob isn't (well, atleast shouldn't be, AFAICT) a problem technically - I think Tim picked the original length for "grab-ability" when the design was still smooth around the circumference.

Exactly how to provide a good grip on a shorter knob might be something to experiment a little with - maybe knurling, or as Tim later did, cut/mill out evenly spaced halfcircles along the circumference. The diameter is a bit smaller than the stock knob, so you need more grip to provide the torque to turn the knob...

/Michael