I had the GP Extra for a long time. Very nice flyer, especially for IMACstuff. I had an O.S. 61FX on it and it would hover and pull out slowly. I did that and TR'd it, but never could get it to harrier. To be fair, I ever intended to use it for 3D so it wasn't setup (CG, Throws) for that. I would say if you want a 3D plane this probably isn't it. Wing loading a bit high, would drop a wing when the stall broke, snapped readily with too much elevator. Now yes, if you set it up right you can push it past the stall, and yes, rolling harriers avoid the wing rock issue completely so you could probably get some 3D out of it but my opinion is the transition in and out of high alpha would be too critical to be worth it. Speaking of HA, I forgot to mention it would do a nice HA KE by appying rudder from a hover, but that doesn't prove anything because a B17 wth enough power would do the same thing.Very nice Imac practice plane, though. the extra, notthe B17
Hope that helps!