RE: YS/Saito 20/20 in OS 46FX
You can only try and see. The 20/20 fuel has lower nitro, but more oil. More oil makes the engine "see" a slightly-higher compression ratio. If the engine run well as you now have it, leave it as-is. Otherwise, try with one extra gasket. Then with just the regular gasket.
We don't have a "sure" answer. It all depends upon conditions and the particular engine.