...while I wait for the right downtube to show up (smallish CX frame + S&S couplers + needs to be stiff = special tube order). Not much to see yet, here's the seat tube/BB shell and a shot of the dropout/chainstay joint. A lot of builders will use nickel silver to braze these in, but I think TIG is more secure (and I'm better at it) so I do it that way.
Also note that I've used a nylon brush on the ST/BB to make it easier to see what's going on. The normal weld discoloration makes it a little tricky to take clear photos.