Ive just seen that someone spotted the vent......strange things happen trying to work on this site...
I went back to my first scan done at a very high photo rate but you can also see what may be a vent in the dorsal surface of the fuse above the wing trailing edge....it would also appear to have been two tone, there is also a diamond pattern on the sides of the fuselage mainly below the cabin but reaching back over the wing.
Heres a link to my Seagull research elswhere...if anyones interested In contributing will set up a thread here as well.
http://www.rcgroups.com/forums/showthread.php?t=474190
mines the Traplet RC version.