I have to agree. The H9 Edge 540 is not made for gas. I ran mine with a Saito 180. It did nicely but didn't waterfall as easily as I would have liked it to. I put in a Brison 2.4 Gas engine. Just made the plane heavier, not necessarily better.
I sold the Edge and bought a Dave Patrick 330L w/ Brison 3.2. That was a much better engine/plane combination, but I'm already set to sell that one too. Since June I've been flying a 1/3 scale H9 Cap 232 with a Mac Minarelli 85 (electronic ignition added). Now here's a combination that makes waterfalls a breeze at half throttle.
Dale