That 6" prop will loose thrust very quickly as soon as any plane speed enters the picture.</p>

Those thrust figures can only be calculated well at static plane condition (no forward speed). Between zero speed and pitch speed*1.1 the thrust falss off to zero. So with a pitch speed of 50 mph, at 26 mph you are at 7lbs thrust. Add some extra drag because the plane has sped up, and you are left with only 6lbs of thrust. </p>

The plane will go vertical unlimited, but probably not like on rails because your prop pitch is too low.</p>