Any welder who is experienced with TIG welding aluminum could weld a plate to your chainstay with little difficulty. However, most bikes are made of 6061 aluminum which has been heat treated after welding to get to a T6 temper, which is very strong. Welding a new plate on there will anneal that area, making it much softer than the rest of the bike. My experience with welding on aluminum bikes tells me it's probably going to be fine without post-weld heat treatment, but you're still taking some risk that the frame will fail there.
I have a Scott voltage I'm working on for a revolt build and I'm wondering if I should be looking into building a new chainstay... I would really like to just get an plate welded to the chainstay. It that doable..? Right now I have It mounted crudely with steel plate for proof of concept.
