The U bends and cutting them up to but weld, works great for DIY. You can get some raw form hooker thu summit/jegs There thinner (18Ga) so lighter but you hear more thu the tubing. The main bad thing about the aluminized is welding it gives off basically nerve gas, and will kill you. So you really should remove the coating were you weld. Not just some scotch bright, or wire wheel polishing it up. You should dig it off and a little of the metal. A coarse sand disc 60-80, or a carbide/HSS burr works good. Check out brents LS1/FD thread on here, the OG neonGLH build, the mark likes little boys cat welding on that beater legacy, My car exhaust if I posted it here, brandons ZO6 I know I posted?
if you wire wheel and or grind the coating off before you weld youre fine. I used mandrel bends too and used a chop saw. I needed tighter radii then the mandrel bends a couple of times so i did pie cut/weld bends, in any event its wayy better than a crush bend. Also, i like using v bands if youre going to be removing exhaust parts periodically instead of messing around with crappy 2 and 3 bolt flanged connections with gaskets… yuck.