Sorry, XP-55 Ascender.
http://en.wikipedia.org/wiki/Curtiss...XP-55_Ascender
The 75 never made it past the no-wing mockup stage and Lou joined the Navy a month after someone fired the gun just as he crossed under it. For all I know, the designation was provisional. Lou worked there in 1943.
He has probably heard and seen things you won't find in books so obviously all that never happened.
I worked with him 79-83 and did PC tech work for him later up to 1999. He was old then, almost 60. He's also in the Delaware Aviation Hall of Fame, he had a long career in aviation in both fixed-wing and blimps. Don't diss the blimps, the stuff he flew makes the ones we see look like toys.