To the OP. Fillet braze. If you do a decent job fitting and wicking in the initial pass it would be easier in my book.
To Henry. Walking the cup is a process that is only used in a very narrow set of circumstances. It's a great skill, practiced by few these days. I started at a place welding machines for processing cryogenic gasses. Everything was pressure tested and cleaned for oxygen service. Big time stuff. I later went into making and fixing airplanes and parts for prototype cars and crazy industrial stuff.
After welding bikes for a few years, I found bike welders to have the highest level of skill on thin material and difficult positioning. Watch the kid at Firefly weld a .8mm wall frame with a few 50 degree mitre angles and you will see. I would place bike welders against anyone and place a bet with confidence.