[vivek16]

The 545 shaft is significantly shorter, it also does not have the splines of the FP. I haven't tried to get a gear on there. I imagine a pressfit will be harder with the smaller, knurlless shaft. Personally, I would leave the FP's in and just use them.

Boco gear: The fischer price gearbox has bolts around the perimeter, just use longer bolts (make sure you don't risk the gearbox coming apart because of this).