I don't think there's a list any where, I never seen one.
Guys have shoerten standard tubes to length they wanted, for the hand gaurd retainer they find the spot welds on the front one and move it back, then reweld it and shorten the hand gaurd to fit.
What about taking the "star" off the M92 piston? I never compared mine to a standard piston so I don't know what else is different.
If turning down the barrel isn't an issue, can you make a piston?
Or how about taking a full length piston, cut the head end off, then cut the shaft to length and weld it back together. If welding is an issue, cut the head off then drill/bore into the head and press the shaft in.