A U Can Do is not a precision flying plane, its noted for how slow it can go and 3-D . Its not at the top of the list, but its probably the cheapest fun. It does knife edge well, even knife edge loops are possible with the right set-up(CG for one)but, it does couple pretty bad so you will have to deal with it one way or another(thumbs or mixing). However, once you deal with it, it will hold knife edge as long as you can and the Do does great S-L-O-W High Alpha knife edge too, probably the best thing about it, except for hovering. As for inverted harriers, I am just beginning to do this and dont have a lot of experience. I have noticed the Do seems to require less throttle or it will nose up and you have to hold in certain amount of left rudder to keep it from spinning. Dont forget, right thrust up-right, becomes left thrust while inverted and since the torque/prop tends to pull left, its worse inverted, so you have to compensate with constant left rudder, except when you are turning right of course. That has been my 2 biggest problems with inverted harriers, with any plane.