I've found that the 12x8 is TOO much for the Supertigre .61 engine.

The 12x7 is pretty good, but it will bog down a bit on verticals.

An 11x7 lets the engine rev up to it's working range and produces good speed, but less thrust.

The ST .60 is only rated at about 1.6 - 1.7 bHp which puts it in the same power range as an O.S. AX .46 or a T.H. .46 both of which utilize 11x6 props.

Assuming the ST .60 actually does a bit better than this, the lower pitch 12" props are about the max.

I've tried the 12x8 on this plane as well as the similiarly sized Extra 300S and I did not like the performance.

I got plenty of speed on light dives, but that was about it. The plane suffered on uplines A LOT.