>I have a rusted seam on the side of a vanagon below
>Flue vent (bottom seam next to LP tank) that is big
>enough for me to put my hand in (4"wide).

Hi Phil,

Here's a link to a site that shows you how to replace the whole panel.
http://www.rustbuster.nl/Bus_zijpaneel/index1.htm
It also has a link to another similar site with some more details on welding
New aftermarket panel available from www.bowwow.ca and I think from the Bus
Depot as well.
My interest in this is not theoretical --- I just welded a sheet metal
'band-aid' onto the same seam on my 84. The band-aid is about six inches wide
and the length of the panel. If i was doing it again (something I'll probably
have to do in a couple of years) I'd buy the panel and replace the whole thing.
This was my first foray into bodywork ---- I'll know better next time. I don't
think this is structural --- but isn't the 4" gap a bit much for bondo ---
you're looking at fibreglass mesh as well I would think.
Good Luck,
Doug Alcock,
'84 Westy
Toronto, Canada