Second what Nat said. I also had new hat channel pressed for my raise--it keeps the stock integrity and leaves you with the flange for riveting the new steel to. Well well worth the cost to get this bit right, imo.
If you do it right, the weld should not be a weak point--its usually stronger than the steel around it.
Plenty of folks have gotten away with doing things less than perfect--but thats because of the awesome redundancy and strength inherent in a skoolie.
I wanted to maintain that strength though, not rely on it to make up for my bad engineering
Best of luck out there, you're in balls deep now!