Yes, the full circle crank fills the crankcase more creating a higher crankcase compression ratio,which forces more fuel up the transfer ports,which may only be open for .001" (one thousanths) of a second,so it definitely helps. My full circle counterweights were solid titanium,not a mash of parts,and they had "stuffed" counterbalance holes,which almost no factory did stock,to make crankcase comp. higher.
Yes how do you balance a 1 cyl. 2-stroke? I had no idea.What I did was made it "same as factory"-whatever the hell that is,and they were good. First time I revved the saw up I held it as far away from me as I could,I was afraid of the crank exploding at high rpm,but they proved strong.
I did modify the big end of the rod for better oiling,in the fashion motorcycles used,and drilled 2 small holes in the top of the rod for better pin oiling,no problems.
The saw factories today only use their "1/3 cranks today because they are much lighter and cheaper to make.
Aluminum flywheels? Considered it but just not strong enough,not even close. My full circle Ti crank was still a few grams less than stock,quite a feat I think.