ORIGINAL: h82crash
This plane definitely needs up thrust on the engine. I've got a standard thickness 1/4-20 washer plus a thin one under the lower standoffs. Looks like about 1.5 degrees of up thrust. What you describe is classic engine thrust issue and has little to do with CG. Go full throttle in level flight and chop the throttle. If it balloons then you need more up on the engine. If it dives then down thrust. Before I adjusted mine, when I put it into an inverted 45deg upline it would just go to verticle. Now it stays on line. That means the cg is pretty far back but not enough to adversely affect most flight. My cg does make it tuck a bit to the belly on knife-edge.
Bob, I've been reading your posts for a long time and I respect your research and opinion, but you must really dislike the way this plane handles on the recommended cg. What is your plane doing? To me, if the plane is stable and doesn't "hunt" (won't stay level hands off) the cg is not too far back. Maybe thrust is your real issue? BTW, why did you remove you Extra from your web page? I miss it.
h82crash - I sold mine in the summer before I finished trimming it. You know, there are some you "connect" with, and some you don't. This was the latter. Great plane, flew a little fast for my taste, but flew very well. I agree that thrust ultimately would have needed some changing, but mine definitely was tail-heavy with the batteries at the cowling bulkhead. It acted tail-heavy, but not real bad.
I've ended up needing up thrust on the SD Yak, the SD Extra, the GP Cap, GP Wagstaff Extra, the GP Ultimate, but NOT the Wildhare Extra 300, or the EF Yak. No pattern to it.... some need it, some don't, and I think ultimately it's probably interrelationships of wing/stab angles PLUS the thrust line.