I have the impression that this engine is better off at a bit higher RPMs and thus with propellers
like 13x6 and 13x7, while 14's are a bit too heavy for almost any .90 engine unless it is a long
stroke engine, which ST seems not to be, and the torque thus is not the best this engine
could deliver, what ever the nitro % is. If you could get this engine at 11000 and even up
to near 12000 RPMs then you see the "ST-miracle".

What do you think about those "ideas" ?

Surely I compare with my OS.91 and I do no think that ST.90 is more powerfull
to be loaded with heavier propeller than the ones I use for OS.91. On those
OS.91FX the experiments with APC 14x6 show good results, and they get
a bit better after  damaged the tip of the 14x6 propeller and balance it</p>

down to 13x6 ...

Cheers,
Nick</p>