Not the best photo, but these are the remedies I came up with for the poor fit.
The starboard side was larger top-to-bottom than the port side, by about 1/16" right behind the cockpit. They fit together pretty well back at the tail.
I made a saw cut along a panel line from the upper rear corner of the windscreen, back to the passenger door on the port side. Then I clamped the two sides together and aligned the top and bottom to fit right. That created a spread gap in my saw cut of 1/16" right behind the cockpit, tapering to closed at the door frame.
I glued a shim behind the cut for it's length, to hold the open gap, and then filled it with Bondo.
I also filled the windows, which are rough recesses for no reason I could figure. My decal set from Mike at Vintage flyer has window decals, which is usual in his sets.
There's a lot to do, but one step at a time.