I agree you should never file down welds beads on thin wall tubing. However, If you don't like the way the welds look you can alway cover them up and smooth them out with some Bondo. You may have to use some wool on the existing paint over and around the welds to create a better surface for the Bondo to adhere to. It may also require some light sanding of the Bondo to blend it in and some local repainting depending on how well you apply it. In the end the Bondo may not cover all the welding bumps but it can help improve the overall appearance. The downside is that it could also cover up any potential cracks in the weld due to the induced stresses of future hard landings. However, I'll bet the stress in this weld is pretty low during normal flight loads so cracking under normal flight conditions is probably unlikely.