Didn't work for me - KNS Precision Adjustable Gas Piston System

I ordered this for my Galil Ace 7.62x39 rifle. Since the piston for the Ace is held with a roll pin, it was easy to remove the factory piston and replace it with the KNS piston. But I noticed that the roll pin size (and the hole) for the KNS is smaller than that for the Ace. As I was trying to find a good setting (reducing the gas flow), I started getting numerous malfunctions. I dialed it back to the highest setting and the malfunction still happened (FTF and FTE). At some point, I couldn't even rack the BCG. After forcing the BCG to move forward and cleaning it quickly, I reinstalled the factory piston and the gun worked again. So I ended up returning this to OPP. Given the stellar reputation of the KNS piston, I wonder if perhaps I should ask a gunsmith to drill a larger hole on the KNS piston (to fit the size of the hole from the factory piston carrier) so that the piston sits tighter on the carrier just as the factory piston. If so, I guess it is a user error. But for now I am giving 3 stars from my experience. Take it with the grain of salt.