I had this bike at Windber in 2011. It had absolutely no trouble with any hills period.
I think part of the wheelie problem, and it is a real problem with this bike, is that when the rider sits on the seat he is at least over or probably even behind the rear axle, the other reason is the gobs of torque this engine makes. This is a great pavement bike but it rides really rough offroad, not much fun. My ol bones need some suspension. I can say it will dump you off real easy.