You’re learning a lot about the reasons why the kits use the cuff-to-hem french seam rather than the bottom hem final seam you’re using. The original process is about as foolproof as it gets. I agree with the reason why you wanted to do it this way though: a high basis weight of insulation.
I don’t think we’re on the same page RE cuff elastic. There should be no raw edges visible using the method described in my last post.
RE zipper installation: Install into the shell with slider, stops, and everything but the topstitching. The shell will look like a completed wind pullover except it will have raw face-hole, cuff, and hem edges. Make a box for the zipper in the liner/insulation. When you’re joining the shell and liner/insulation wrong sides together you won’t be able to sew the zipper, so just do the cuffs, hem and the face hole of your hood and stop at the zipper. In the regular Kinsman Pullover procedure you’d have sewn up one zipper edge, around the collar, and down the other at this step. In your case, the bottom fronts and the zippers are already fixed in place which causes problems for the regular way (note that it would have worked if it were full-zip). Once you turn the jacket right-side out you sew through the zipper tape from the shell side into the box to secure the shell and liner/insulation at the zipper, right next to the shell fabric but in the black zipper tape using black thread so it’s invisible. You then topstitch through the shell/liner/insulation from the shell side using shell colored thread in the spool and black in the bobbin.
