I've got the shell off of my 1950
Flying Cloud #7002. The floor it was lifted off was almost entirely rotten. I do have a decent piece that was the rear curve. But I'm pretty much going to be starting from scratch to determine most of the footprint of the new sub-floor.
I can see that there is some potential flexibility as far as exactly where the edge of the floor/c-channel could wind up being. I suppose to some degree it doesn't matter exactly where it lands as long as it is all fairly square and level and the width is about right. I recall the width was not consistent front to back originally.
My plan is to set the shell on the new floor and trace/draw what looks like a symetrical and square shape for the floor/c-channel. I'll cut the shape out then I'll set the shell back on and see how it fits.
I'm sure some of you have some tips for me. I'd like to nail it in one shot if possible. I'd rather not have to set the shell down more than twice if I can help it.