Nobi,
Nice looking model!
I've collected information on flying wings over time as one of my ongoing areas of interests. A couple of points on the XP-56:
o small circles around the fuselage in the middle of the vertical stabilizer
are exhausts for the air cooled R-2800-29 Pratt & Whitney engine.
You might consider adding small circular extensions with a trapezoidal
shape as viewed from the side.
o The fuselage does not fair smoothly into the propeller spinner. An
annular shaped air duct vented around the spinner.
o An antenna mast was located on the top of the cockpit canopy just
forward of the first side reinforcing section. An antenna wire ran from
the tip of this mast to the upper part of the leading edge of the
vertical stabilizer.
o The tip of the dorsal fin (fin on top added to the second prototype)
and the serial numbers were painted yellow.
o Serial number 238353 was painted olive drab upper surface and gray
lower.
If you need further assistance just contact me off line.
Best regards, Gil