The fairing I'm using allowed an old school 70's road racing factory 750cc twin to go 160 mph with 90 hp (no tail,, just the standard seat/tail cone of the day).
My guess is that your 650 in making 70 to 80 honest hp (any more and it would most likely be a grenade) and that tail is maybe worth about 20 hp...
Those are real strong numbers you have run,,,good job !
The air density assumptions could be a little off in those programs and that will make more difference than it first appears....
When I was crewing Reno air racers, we watched the density altitude like a hawk.... Humidity and temperature change it a lot... as the DA goes up the air mass to the engine and cooling system goes down, but so does the resistance of the vehicle moving through the air... Just how much one washes out the other can be quite vehicle dependent to get calculations to output exactly correct numbers.
Robert