ORIGINAL: Andy P.
It needed a bit of up trim to keep straight hands off, and when inverted it needs a fair bit of down stick to keep level, indicating it's a bit nosey.
Is this cg assumption after checking the 45 degree up with half roll to inverted at full power? (the model should just keep going on a 45 line without any need for down elevator) this is by far the best way to check your cg, after all it could be a thrust line issue, needing up trim and the subsequent excessive down elevator during inverted!
Just a thought...................
It probably is more thrust line than C.G - but I couldn't be bothered with it. The original balance point was 110mm and I needed a few grams in the nose to achieve this - despite having the battery pack located all the way forward. I've now removed all the added weight so the C.G is back a bit from specified and the up elevator required in inverted is now less. The fuel tank is also situated forward (like most nitro planes) so getting it "hands off" all around is not possible for the entire flight. It's really not a big deal with this plane though - still flies great.