Yup Chinese am are different.there are a few brands that differ. I grind the square to suit.carefully of.course. only oother option is older am rings come up now and then or genuine NOS again if you can wait till they come up. Other option new piston will suit the am rings you bought(square peg). Yup its getting harder to re use sh pistons but always a a way around it. See how ya go and easy on the grinder as it only takes a minute amount to get the arc.
