Sounds like a good solution.
It's over twenty years since I built mine, but I seem to recall having problems with the seats, and had to move them to allow the fuselage halves to join properly. I'm guessing the resin cockpit sidewalls are fouling the seats, and maybe should have been thinned (or the fuselage thinned) to allow a better fit.
I made oxygen bottles from Milliput, and they're mounted, as you rightly say, behind the cockpit, almost parallel with the top turret.