G21-35 Head

I just won a ST G21-35 off e-bay. It is a wide bypass, early version not a PDP. It had a RC Carb. which I have taken off. I noticed that the head set rather high above the cylinder, I removed two copper gaskets and had what I thought was an extra aluminum gasket. Turns out that the head is machined such that there is the equivalent of a .010 to .015 gasket machined on the head and the squish area is larger. It was my impression that the flat piston G21-35's were not really suitable for RC until the advent of the PDP versions.Does anyone have any information on this setup?

The last G21 .35 I acquired, in fact the one you transported to Tulsa for me, was an identical set up to the one you describe, apparently original carb with butterfly device, etc. but had one aluminum gasket. I am assuming this is a factory RC set up. I am thinking this engine came in a red box but I don't recall how the box was marked and I am not able to locate it.
It ran pretty well on pressure with the standard pressure venturi but was not exceptional.