Removed the spacers and sanded to profile. I am somewhat mollified now. It all looks lovely and only took a little bit of fill really. Sanded the gap flat against the fuselage, and for a 1mm gap aft, with 240g wrapped around a cf spreader. I'll need a tiny bit more FILL for low spots and to achieve the 1mm gap I'm after.
There is only a small area on the fuselage bottom that will need FILL and WIPE again. I'll do that next when I tackle a wing. The cowling can wait until I have them both fitted and confirm I'm happy with the part line.
