This thread has provided me with more options than I thought probable.

I don't understand the TIG vs Lug discussion, nor the message in Thylacine's posted photos.

I had assumed that lugged frames, albeit slightly heavier, do not heat distress the tubing as much as does TIG welding.
I suspect I don't understand TIG welding.

I'll do a quick search on TIG welding, and perhaps someone can make a few illuminating comments.