Flybug,
Its been said several times already in this thread but I think the main gear are located too far forward. Perhaps there was a mistake when transfering a dimension to the fuselage from the plan or something. The designer wouldn't locate the main gear inside the CG range. Duraplane trainers have been around since about 1990 so I doubt an error that big has gone undetected without a revision in the plans or instructions. I bet if you retrace the build sequence you'll find something.