Thanks for replying Mark.
The only floor channel that I was able to salvage was the curved pieces. When I put in the replacement channel for the straight sections, I am using the line of undercoating/clean aluminum that appeared when I removed the old channel as a reference.
Did your shell extend below the decking?
In analyzing the support I used for the shell - I screwed 2x4's lengthwise down each side - screwing into each stud, then did cross bracing for jacking and stability. After thinking about that, since my original floor was gone, I had some studs/floor channel resting on the outriggers, others were not touching at all - it would seem that my shell wasn't level/straight when I braced it.
Can I use the bottoms of each stud as a reference for straightening the shell? Should each stud rest right on the floor channel, or are they sometimes floating?