Excited to see the progress on this! I think its a much better size for 95% of GT owners looking to upgrade. The smaller rotor pack should make for some better throttle response and the extra 150-200 hp over stock is exactly what the car needs.
Good points, but I think the targeted HP is more that you are citing but can always be de-tuned. We've had more that 30 GT's on the dyno and we've had the opportunity to get baseline (stock) HP runs on the majority of those before any power adding modifications. As everyone is aware, the OEM ENGINE HP rating for the GT is 550HP. On a dyno measuring rear wheel HP (RWHP), stock GT's typically are right around 500 RWHP (an approximate 10% drivetrain loss).
A pulley tune kit will generally yield about 600 RWHP - a genuine 100HP more than stock and which really wakes the car up and is one of the best power-adder values on the planet!
We've install Whipple SC in the past and with a pulley sized for ~21psi, we've achieved RWHP of just over 800 RWHP. However, with the Whipple, this is at the limit of the OEM fuel system. Any higher, and you would have to consider larger injectors and larger fuel pumps, etc.
With the set-up that B.M.F. has come up with - the efficiency of the SC is likely MUCH better than the Whipples of yesteryear. As such, he will have the ability to select a pulley size that can achieve the requisite boost to hit a target of 800 RWHP. Because of the greater efficiency of the blower, an 800RWHP car will have a wee bit of headroom in the fuel system and this should be a very good set-up for owners who want the most power. Note that this will be 60% power increase over stock. The only downside of this is the fuel requirements ad B.M.F.'s testing will tell us, but I'd guess that 94 octane would be a minimum... if not 100.
If he chooses to, B.M.F, would also have the ability to provide a 650-700 RWHP kit. The only difference would be to have a larger pulley which would generate less boost - say, 17 or 18psi. With the increased efficiency of this SC design, there is potential to have this set-up running with a more readily available fuel octane of 91-94. This set-up would be 30-40% increase over OEM HP and might very well be the sweet spot for a very reliable, daily-driven-capable, GT.
Exciting times for all!