During some of the pre-game I worked on the Mustang. While waiting on the replacement wood to arrive, I worked on the fuselage a little. There's a made in America lightweight filler that I found at Home Depot. It's their brand, HDX. It's very light, dries fairly quickly, and is easy to sand. I used it to fill the seams where I cut the sheeting to make the curves on the bottom, back portion of the fuse and also along the front between F2 and F1. There's a floor that goes in behind the firewall, Fb, that I cut out of 1/8th ply and glued to the edges of MS. When there's a plywood to plywood joint that has to be glued, I use Gorilla Brand wood glue. Its an aliphatic resin that sets up pretty hard. It's sandable, semi-waterproof when dry and seems to bond exceptionally well. It slows down the building process a little, because you have to clamp it and then exercize a little patience. I have found that it's best to leave it overnight, just to be on the safe side.