OK, 60" tall by 96" long, ribs at 24" intervals interrupted by the window opening...no problem...off we go!
Got the frame 80% completed when it occurred to me I had never had anything bigger than a 4 x 8 sheet of plywood up the basement stairs...

1 x 2 framing bends remarkably well...and squeaked up the stairs with NO room to spare. The rest of the framing was completed in the back garden... after lighting a candle to whatever saint watches over fools, old men and TTT rebuilders.
Just a word to the wise and a bit of a tale told on myself...make sure you can get the finished item OUT of the workspace even though you can get the materials in!
Alan