I know the 920 and 920 Super are 54 x 1.5mm.. just had one of each apart, Pistons are identical, though the jugs are different.. the 920 doesn't transfer through the piston windows, the Super does.. and makes a whole lot more power for it...
I don't know about the 910. From what I read on Acres site it's the same bore and stroke, probably the same piston design, but it doesn't mention ring thickness there.