These are certainly interesting questions. According to the 6-10 documentation I posted earlier, the connecting rods are interchangeable on the crankshaft listed, and presumably on any crank that would use either one. A later 7-10 crank assembly with either rod and piston configuration should interchange.
Swapping connecting rods in order to use the full skirt piston would evidently reduce squish by 0.010 according to Mark's calculations and would need to be taken into consideration, but probably only marginally. I've never measured squish on a Mac. The different rod lengths should be offset by the different pin diameters (and locations) to effectively provide the same piston stroke.
Another possibility is that the cylinder was simply changed and that's been the problem. That's really the main unknown factor now. This theory would only be applicable if a full skirt piston is actually required for the three finger transfer cylinders as has been my theory..., misguided as it seems to have been. It has finally become quite clear to me that the piston originally called for in a 10 prefix 600052 7-10A is indeed a windowed design after all. The correct piston for the IPL of this saw is on the way. No way to really know if the cylinder is correct (or original).
The only other thing left is whether a windowed piston should work just fine on all 3 varieties of transfer types now known to be used on the 70cc saws. Indications are that it should, but I've not seen definitive evidence that is the case. It certainly would not apply to the earlier 70cc saws with small pins. I'm unaware of any windowed 2" pistons with small pin bosses..., only full skirt versions..., which are typically what is found in the three finger transfer cylinders.
