The more layer, shims ect, the less strength you will have.
Mickslife.
Please look around this site before thinking welding thin, galvanized metal is stronger than other methods. We have covered this repeatedly. Long story short, a armature welding outside with substandard welding equipment, with minimal experience leaves a massive margin for crappy welds that can and will break.
You also risk damaging the original hat channel supports beyond repair.
Riveting is the way the bus was made for the same reasons airplanes are. Armature DIY people can set good rivets and bolts in almost any environment without failure.
Welding needs to be done right to be strong. Done wrong, it's asking for a disaster.
We don't need to make skoolies even harder to insure. So please guys, lets do these roof raises the best way we can.
Nat