Matthew,
You're asking too much from a 10 cc.
Here's my RV-4


I started flying it with a Super Tigre .91 nitro.

Turning 10,000 RPM Speeds were always below 40 mph (I've full telemetry in the bird) performance was Ok but not great.

Then I went to gas and a 15cc engine

Speeds went to 60 mph a 14/6 Vess prop turns a little over 8000 RPM

I believe the plane would fly a much better regime if a 20cc were in the nose. The 15cc gives good take off, climb and overall performance, but will not hold vertical climb for more than 5 seconds.

My observations FWIW is that the EVO 10cc, compares to a hot .61 engine but that's only with the best possible propeller match up. Unless you are talking a different RV-4, mine is the now discontinued
Great Planes 72" wing span plane.

KKKKFL