Looks like it might be a Mercator. If so, I have been researching that puppy for a long time and have a ton of references, including camera shots from the NATOPS manual which shows a lot of detail; essential though is Ginter's book on the P4M. Looks that you have gotten a long way through it however. The tail though is looking a lot like a Privateer's and the fuselage is too boxey(?). Few pitfalls, one being that the wing changed airfoils at the outer wing attachment and had to incorporate a 'jog' to mate the two different contours. The change in airfoils would not be that obvious but the change in leading edge line is noticeable. Whose plans are you using, Aaron? There is a pretty good one at:
http://smm.solidmodelmemories.net/Ga...e.php?pid=3429
The Solid Model Memories site is a gold mine of drawings, though look out for W. Nye's stuff - some of it is pretty inaccurate.