The way I understand you are doing it you will have a bunch of little pieces of metal showing where the holes are on the inside of the tub??

If that is acceptable to you it will work fine until you stress the bond somehow, either thru vibration or impact. First the filler will crack at the hole, then the patch will fall off. It might take days, or years to get to that point.

I have seen some bolt holes filled with bolts, then painted. It is a rustic look, but better than holes in most cases.  SOme guys use stainless or chrome bolts like bumper bolts or small similarly shaped bolts.

In the used car biz, aluminum foil tape is applied from the backside, the hole is tapped inwards with a ball pein, and the hole is filled with fiberglass reenforced filler like Kitty Hair or whatever they call it nowadays.  Again, the inside is sorta ugly looking, but you can get the outside to look nice. the same failure ad your JB weld will happen eventually. It may be decades or weeks, depending on how much surface area the KH has to stick to. The really cheeeep used car guys use newspaper slathered with filler to make the patch. I did a Subaru like that once for a buddy and was amazed at how long it lasted....in the  NY rust belt too.. We saved a rotting hulk of a car for a couple more years that way.

Smaller holes can be soldered up with regular acid core plumbing solder.or body solder. It is a little more durable that way but then you have the lead safety issues.

If you want to minimize the amount of work and aren't a purist (sounds like not a problem) the hardware stores sell those black plastic hole plugs.  They have the "ribbed" ends which when you push them through the hole the grab it and are secured.  They come in all sizes and are usually in those flat boxes back with all of the misc. fasteners.  You can cut off the plastic on the back side of the hole and they don't really look too bad - just a flat raised bump, and you could paint the color of the jeep.  Not saying this is the best solution, but it is a quick, inexpensive one.

You have a welder!  Use it!  
Flux core or MIG?  You can do it with flux but a MIG set up is easier (to me).
1/2" is pushing it, Ive been lazy and filled up to 1/2".  That and anything bigger, you should make a plug disc and weld it in.  For smaller stuff, get a peice of copper and use that as a backing.  A piece of flatten copper pipe works good.  Then I grind with a wheel just before the surface then switch to a flapper disc to smooth the weld.  I dont know if you can be that good at that point to get away without body filler but I always use a little bit.

Practice on something 1st

Just the smart mouth in me talking here, but you could ue the bolt holes as pre drilled accessory mounting locations.  That way when you figure out what goes there, the hole is already drilled....not a good idea huh.

I've been filling holes in my body all day today.  I have a little flux core welder that is just a bit too powerful.  I have it turned down all the way and still burn through my sheet metal.  Never thought there would be a day I wished for a less powerful welder? Oh well, today was the day.  I found a few tricks that are allowing me to build up the weld as I fill the holes.  I'm going to have to grind down a bunch as a result but it should turn out OK.  Now if I could just find that PO and ask him why he thought it was a good idea to weld in galvanized steel with brass brazing rod to patch the floor... 

Good stuff! 
Thanks

macrisel wrote on 07/06/12 at 16:47:46:


Says the guy that knows how to weld