Replacement segment seam sealing and rivet sequence

[binkers]

I am in the process of replacing 2 rear corner segments on my '93 Excella. I am ready to permanently affix the lower segment to the frame (upper to follow) and curious about the proper way to seal the vertical lap seams and horizontal rib contacts. I removed the adhesive tape material that was present between the original segments and ribs but wondering if this or seam sealer tape should applied between the frame and new segments? I should also add that this is an exterior-only repair, so I have no access to caulk seams from behind once in place.

I am also curious to know if there is a preferred rivet sequence for these corner segments. Start in the middle and work towards the vertical lap seams?

A lot of work to get to this point and don't want to blow it now...Any advice, tips and tricks on this is much appreciated!