Stéphane,
I just chanced across your work and wow, am I impressed. Wonderful stuff, lots of fun. I'm a big fan of prewar U.S. designs (XB-19, Seversky P-35, Bell YFM, etc.) as well as oddities like the Vought V-173, so was glad to see variations on some of those types represented.
I have two nits that might interest you. 1) The inlet cones on the SR-72 really must project ahead of the leading edge of the wing, as on the SR-71. Otherwise they won't be able to do their job, and a supersonic shockwave will cause unstarts or worse. 2) The cruciform tail on the Fairey F.30 (nice that you named it "Arrow," a nod to the DO 335) requires a three- or five-bladed prop. Dornier recognized that, as did Molt Taylor with the Aerocar (triplane empennage, two-bladed prop). Put a four-bladed pusher prop on a four-plane empennage (or a three-on-three), and there will be aerodynamic/structural hell to pay!
BTW I'm a big fan of PSP, have been using it since version 3 (now on v8, pre-Adobe) and have hope to keep it as long as Microsoft allows!
Cheers and best regards,
Ramblerdan