You get into diminishing returns with bigger block engines in a FB........excess thrust over drag vs speed is not a linear function but approaches a square function due to induced and parasitic drag as well as cooling drag(turbulence in our intake ducts, bypasses, and tailpipes).....so to double speed, you need not 2X the power but 4X the power.......add to that the extra power needed because of increased weight, which is also a square function, and you reach a terminal velocity which is hard to exceed, no matter how big a block you put in. Plus the big blocks suck more gas. But what the big blocks give you is exceptional Hill Climb ability.....the old power to weight thing. My BVM Phantom at 27 lbs dry with a 35 lb Titan is an Unlimited Banshee in the climb, whereas my BVM F-100D at 38 pounds dry with a 37 lb Pegasus runs out of gas half-way up the same hill.....

Talked to Tom today.....he is now flying with some crow in the ailerons, 40 deg flap, and, of course, the bigger rudder for increased stability in the down and dirty configuration. But it still stalls at an airspeed in the high 40's, so chop and glide 75 yds out like a Boomerang is not suggested for landing.....best to fly it with some power on until mains are about to touch.