So... I've been working on a suitable design for connecting the upper tranverse frame to the lower frame rail. The main issue is how to get it welded as securely as possible because having it up against the back of the firewall and against the sheet metal connecting the B pillar to the lower frame rail (not shown in the drawing), access for full perimeter welding is quite limited. In the end I opted for a simple angled plate that caps the lower end of the vertical support as well as provides a somewhat secure anchor between the vertical support and the top and inside face of the lower frame rail. With it all tacked together, the entire assembly can be removed for welding completely around the perimeter of each joint and then returned to the chassis for installation and welding were possible. If I had more nerve, I'd remove much of the firewall sheet metal to allow for structural welding and then return the firewall sheet metal afterwards.
While I spent most of the day crouched in the engine bay fitting and refitting steel, I also fitted some cosmetic sheet metal on the inside face of the lower frame rail. ( It's remained uncompleted since I did the frame stretch). I'll complete the final welding and finishing when I complete the final welding of the transverse frame and supports.
Its quite tiring climbing in and out of the engine bay with step ladders all day long with gloves and welding apron on. I think if I ever do another Fiero like this, I'll build a permanent patio around the entire car with proper stairs and then just lift the car out when its done. Then put a hot tub in the hole.
Here is the drawing of the vertical transverse frame support and a picture of the parts tacked together in place. The camera flash sure lights up the ugliness of the unfinished welding.
Not sure if this counts as "making progress" on the project, but I did buy a rack for the new wheels. May as well have a nice place to store them as its going to be a long time before they are rolling down the road.