Spent about 4.5 hours in the garage today. Got the sill plate patch welding in and then cut out another hunk of the bed floor. The middle floor brace was more solid than I expected. I cut out the outer six inches or so and fitted a patch for it.
Then I covered it all in POR15. I'll let it dry over night and weld it in tomorrow.
I then turned my attention to the end cap, cutting two pathed for it and getting one of them welded in place.