Here's my 18x12 Zinger 4 blade on my RCV-120 equipped TF P-51 (camera didn't like the red too much[
]). It has one flight on this prop at a bit over 11 lbs. I thought it flew pretty scale like, but I didn't put it through too many manuvers. I folded the gear on landing when I slowed it down a bit too much about 2 1/2 feet off the ground and was hessitant to give it much throttle for fear of torque rolling it into the ground (it didn't have that tendancy in the air, just hear horror stories). I have since put it back together and moved some stuff around and lightened it by 12 oz., so hopefully, the next flight will be more successful!
To me, the big prop is part of the beauty of warbirds and I would have a hard time with anything much smaller, although I do have a 15.5x12 4 blade APC to try out also.