all of these posts are correct. from what you described in inverted
flight i would presume to say that your cg is not the problem. if you were nose heavy you would need excessive dn elevator during inverted. what size engine and prop are you using?
what type of rpm's are you turning? contrary to popular belief,
knifeedge flight is dependent on torque more heavily than airspeed. on your prop, length represents airspeed and pitch
represents torque (this is a loose analogy). if you are propped
for all out speed, you will have very sluggish vertical performance
and hince, no knifeedge. if you're rpms are high in the engines
suggested range then you are probally under pitched. if you're
using an 8 or 10 pitch, then try a 10 to 12 pitch (respectively)
also keep in mind that lugging the engine with a prop that is too
large will cause these same symptoms and also cause heat damage to your engine. also remember that some planes although designed with pattern or aerobatics in mind, just dont
like knifeedge flight. good luck and please e-mail me and let me know if this is any help to you.