If the model balances (at a slightly nose down angle) on your fingertips at the CG given in the instructions then I'd trust that. If that also agrees with what you get on the CG machine, that's great. If the model still falls back on it tail, then it's one of two things:

1. The CG given in the instructions is wrong. It happens. The CG should be at no more than about 25-30% of the wing cord.

2. As Campgems says, the main gear are too far forward.


I've never seen this type of trainer before, so I'm wondering if it would somehow "pull itself upright" with the engine running.