RE: Saito 62a vs OS FL 70
Chistech - you're absolutely right - you can compare different engines.
Here's an FL70 benchmark I can offer that you may wish to use as a comparo.
A club member had one mounted at the 7:30 position in a scale .40 size GeeBee - an application more demanding than this on engine reliability I can't think of right now.
Once he'd broken it in and put a fresh OS type F plug in it, this engine never let him down with a dead stick. It pulled an MA black 12 x 8 K series prop at just on 10,000 rpm static.
If you have one of these props in stock, fit it to your .62 Saito for a direct comparison.
FWIW, I don't think there will be much difference in power output between the two. IMHO, picking a winner in outright power between these two would be a dice throw.