96 XJ here and I'm rebuilding what was once a huge hole in one of my rocker panels. I've riveted in 1/8" diamond plate aluminum for the backer support and now I've got 2 good coats of bondo on there. I'll end up going over the 1/4" thickness limit for bondo, oh well.

So my question is...how do I go from where I am now on the left side of the pic to building and smoothing this out so that it's paint ready and in the shape of the rocker panel on the left.

I've got a can of color matched red and high build primer on the way.

 

JMO, but what you are doing is a waste of time, energy and some money. That will not last long at all. Can you weld? If so, get some steel, flat or some square tube and weld new rockers the full length. Or if you want it to look factory, cut the rocker out cleanly and weld (or have it welded) a piece of steel on.

Then finish it out with a skim coat of product, sand, prime and paint.

 

I agree with the previous poster, and there is too much flaky rusty metal left, it will rust in no time

If you cant mig weld, then I would buy a cheap inverter ARC welder, weld in a section of rectangular channel, I thinks it 6" x2" they use (check archives) then rivet sheet metal where needed

then bondo.

You cant bondo over rusty metal, it only lasts about 1 year

sorry

 

Sorry, but that looks terrible. Cut out a little past the rust so you know you have all of the cancer out then weld a piece of steel in. The guy above has it on point.

If welding is too expensive, a few rivets and seam sealer will look better than what you are doing now.

 

Seriously, cut that cancer out and weld in a replacement. That's the worst repair attempt I've seen in a long time.

If you can't do it, take it somewhere.