My Bobcat 50 won't knife-edge (with an ASP52 pushing it along).

One of the problems is that there's only a single-bevel on the rudders so the throw is somewhat limited.

As others have said -- they're fine for keeping the nose straight in a cross-wind landing but other than that the rudders are not essential. If I didn't have any servos suitable, or if I had a CG problem I'd just leave them out.

My Bobcat is still flying real funny though.

At low airspeeds it wants to climb like hell -- needing about 1/3 down elevator to stop it going vertical if you open the throttle to full during an overshoot (for example).

Once it gets flying speed up though, it wants to tuck under.

It's also mondo-sensitive to elevators on the approach (to the extent that getting the flare right is more luck than skill). However, if you reduce the elevator throw it runs out of authority in turns and when pulling out from steep power dives. The servo on the elevator is rated at 3.5Kg/cm (45oz/in or so) which should be plenty-strong so I don't think it's blow-back causing the problem.

These are symptoms of a rearward CG but mine is right on 10.5 inches from the LE as recommended. I'll try some lead in the nose and see how it goes.

Right now, at 2/3 throttle it flies straight and level with the elevator perfectly neutral relevant to the tailplane and dives when rolled inverted, needing about 1/3 down stick to hold the nose level.

We had a radar gun at the field on the weekend and my Bobcat was only good for just over 100mph. My (slightly modified) trainer is good for more than 110mph so the Bobcat isn't exactly as fast as I'd hoped.