Yes it can knife edge loop all day long.... It didn't when I had an MDS .48 of the first one. The big motor/big prop gives the rudder lots of authority. A 3-blade won't cut down on vibration, that's a function of balance and RPM. Balance the prop and It'll be fine. If not, try using an out of balance prop and "timing it" so that the heavy blade is opposite of the cylinder when the piston is a top dead center (180 deg.). That'll usually do it.
I've seen a couple of postings bashing the Pizazz but the overwhelming populatiry of them would suggest otherwise. I probably only have half the flights on mine because everyone else flys it!
I did replace the Hangar 9 C/A hinges after they failed in the first season. My left aileron fell off in flight, only being held on by the clevis, didn't notice much except that it rolled funny until I landed. I used Sig C/A hinges on the second airplne.
A lot of how the airplane tracks can be trimmed out. i.e. if the plane won't hold a knife edge move the CG back... If it tucks to the gear in knife edge (it will) mix some up elevator to rudder and try using less rudder (that's what I said). At large deflections the rudder can deflect the airflow over the top of the stab at high angles of attack. Since there is generally more rudder above the stab than below it you end up with low pressure on the top (of the stab) and the plane pitches to the gear. Mixing up elev. increases the pressure on the top side...
With the thick wing it is very forgiving in CG adjustment. I have the throws up as high as they'd go (on high rates), cg at 30% of MAC and it flys beautifully.
Some favorite manuvers:
Rolling Harriers-1/4 throttle, full left aileron (low rates), bang the elevator to keep the nose high or turn, adjust the throttle to clib or decend...
Waterfalls-50% Flaperon mix (down aileron w/down elevator and vice-versa) pull to vertical hover, full down elevator and 3/4 throttle...
TR launch-with the .91 I hold the plane vertical by the canopy (glued and screwed), full throttle, let go, fly the torque roll. It usually starts rotating as soon as it leaves my hand...
I wish it were warm!