A little more progress. First I finished the rib tie points by welding the 2 2x5 pieces together with a bottom plate, and thru bolting with a pair of 3/8" grade 8 bolts with nylock locking nuts...
Next I cut "fingers" into the edge of the upper and lower sections...
I took some flat nosed lineman's pliers and bent the fingers and then clamped an aluminum bar to the top and bottom opposing fingers with a piece of steel cut out the section of roof that was removed. This piece straddles the cut between two fingers. I then welded the pair of fingers together with this piece...
The bottom picture shows four fingers chained together with the fifth one ready to weld. When done I'll have 2 parallel rigid lips to rivet the transition piece to.
Onward Ho.
Casey