RE: DLE 35RA going to 3 blade prop
BubbasanJohn, as stated above the wide blades put a heavy load on the engine. The Xoar props have narrower blades and the same "size" prop will turn up better rpm getting closer to the engines rated power in flight. A heavier prop might accelarate from idle to full power slightly slower but is not really an issue. Also you can get a slower smoother idle with a heavier prop.
Just to compair, I ran the RCGF 17-10 three blade on the G-38 I'm planning on putting in the ESM Hellcat. The DLE turned the prop 6,000 rpm and the G-38 6,450 rpm. I think with all these engines you need at least 6,800 to 7,200 rpm so when unloaded in high speed flight you will be getting around 7,900 to 8,300 rpm. You certainly don't want them turning over 9,000 rpm unloaded. I think that is too much. Just my opinion.
I still think the Xoar 18-8 three blade would work for you on the Hellcat and look close to scale. The 18-10 will give you more speed but I would rather have the flatter pitch for low speed thrust in an emergency.