A recent experience reminded me of this thread and Nat's recommendation that amateur/wannabe welders use bolts instead (along with proper channel material):
'Bout a month ago, I was swapping bumpers between two Dodge B-series vans. Some bolts on the donor van wouldn't, well, unbolt, so long story short it was easier in the long run to cut the bolt heads off. Since the donor van was a parts vehicle it wasn't so critical I left all the bolts intact. And damn
, getting those bolts cut was a b**ch! On that steamy day I thought I'd sweat enough to make a replica of the Dead Sea on my driveway.
Based on that experience, I think that if a car hit the tail of the van sideways, at the edge of the bumper, the result would have been a mangled bumper, held fast in place by those tough bolts.
Oh, and there is a grading system for bolts, designated by marks embossed on the head. Some research via mechanic's books or Google will help you avoid inadequate fasteners.
Originally Posted by nat_ster
I feel cutting the roof compromises structure.
Think about the arch. Then you will understand.
When I cut my hat channels, I had sections of floor drop. They were being held up by the roof.
The roof being one piece is the strongest part of the bus.
The roof needs to stay one piece.
Wayne Corp. used stem-to-stern metal skins externally and internally, at least on its Lifeguard series. Though the ostensive purpose was to keep the thing from splitting open and creating flesh-slicing edges, I'm disinclined to cut-and-splice my Lifeguard's roof any more than I'd absolutely have to.