Thanks for the welcome. Yes I heard that some people develop a skin sensitivity to nickel bronze, pity because it forms a very pure weld. I used nickel bronze for my first frame as I had used it quite a bit as young fellow in the motor racing business on cromoly tube chassis. Also, it was Jim Cook's filler of choice. I did consider TIG for my first frame and even had a lesson from an ex F1 chief engineer. The lesson went very well but I decided there would be far too much practise required to become proficient using TIG. Regarding Castolin 38230 (Ag 30%), my guess is it will be much easier to build a fillet than SIF No. 39 (Ag38%) as it's flow / fluidity is rated less. The key question for 38230 will be control of porosity and ability to post rework a joint without introducing more porosity. If the porosity is controlled as well as SIF no. 39 and you can weld more up slope and down slope then it should be a goer.