Finally got to do a bit more work on the RD. Tacked in the backbone and the seat loop.
Sat the ratty old XR copy seat that I had and the brand new Knight style tank (many thanks to Firko) and it doesn't look too bad. The tank isn't the best fit so I might make an alloy one later if time permits.
Still need to gusset the steering head and then finish removing all the redundant frame brackets and make up brackets for the rear shocks, coils, footrests, number plates, tank, seat etc. Once that's done the pipes will need to be made, then the engine can be pulled down and rebuilt.