I just bought one of these planes last week and my first flight had me on my toes. I leveled the elevator when setting up but when I took off I needed a mass of up trim for level flight. My instructions only gave a 100mm cg location but I worked that out to be 37% of the constant cord wing , so I set mine on the spar about 80mm back.
Landing was a task because it sank like a brick when I took the power off. I could tell this plane was very nose heavy. The stock tank that was supplied is too big and I did not need all this fuel for my asp 61 four stroke ( it would fly for well over half an hour) so I put in a small light tank. I also put the elevator servo in the tail and rebalanced, now I have 85- 90 mm back and the plane is much better and will land at walking pace. You can really pull back on the stick for a great three pointer.
Even though it flies well now I was amazed that I still needed all the up trim I had before, so I flipped it over inverted and to my surprise I only needed the slightest amount of down to maintain level inverted. This has to be an incorrect wing incidence, it pitches to the canopy badly ( I know this is usual for this type of plane) but if I alter the negative incidence I can take out all that up trim.