Giant Stiletto looks great. Tons of space. Built in jackshaft.
I am only getting 30 MPH using your gearing with this:
Rawge's Mini Chopper jackshaft calc:
(6000 RPM with 24" wheel)
With 45 MPH gearing you are going have pedal more to have a decent clutch life.
Wind resistance goes up with cubed root of speed.
But with such a long bike you could lay down to cheat the wind.
Best of luck.