Another item, and this comes from a respected heli pliot at our field, he says any nitro over 18% is really just adding cooling capacity.....not power.

For some engines this seems to be true. IE: Magnum and most 2 strokes. But on the 4 strokes (Saito & YS) I've seen a 20% or more increase in thrust according to my trusty fish scale. That's pretty impressive.

Thanks
Barry