I don't know how much compression is to much but after a few tanks of gas and the rings seating,I finally got my compression gage out and the compression sets right at 200 PSI. ( I triple checked it ) The aftermarket piston has a slightly higher dome which accounts for the extra 25 psi increase. I gotta tell this R16 is just a beast will all kinds of torque and wants to be run on the very edge of being lean other wise it looses power. I use HR1 mixed at 32.1 for insurance. This is a definite keeper. Now it's on to the 3.7 rebuild.