e-coat panel sandwich - how to prep?

I'm getting closer to start assembling a 3 panel thick sandwich at the rear lower corner of the window frame.

What's the thought on preping the panels?

* leave it e-coat except where the welds are
* clean it all and weld it up as bare metal
* or?

Didn't have the best luck with weld thru primer so far, but apparently haven't got my hands on the right stuff yet.

Sand down the ecoat, skip the weld thru, make sure all welds are closed. Lots of skipping and air blows, grind welds, avoid bluing the welds. Measure your glass for proper fit many times. Once your done apply epoxy primer. Then do your mud work over the epoxy. Use the water proof mud.

The E-Coat provides the best corrosion protection available. I would leave it on where it makes sense. The spots you will be welding will need just that area stripped to clean metal for the best weld. You'll want to apply a weld through primer to the bare metal prior to welding. After all your welding is complete you can then scuff with usually 80 grit and apply your epoxy primer or fiberglass reinforced filler as recommended by their tech sheets. As an example, the epoxy I like to use says scuff the E-Coat with a 3M Red 7447 pad prior to applying the Epoxy and it says sand bare metal with 80 grit for adhesion. Read the Tech sheet for yours to see what the manufacturer recommends for their product. As far as the filler goes, again first read the tech sheet for your product. I use Evercoat products such as fiberglass reinforced and Rage. If I'm filling the weld areas or high stress areas I use the fiberglass reinforced since that's what it's made for. It is fine to apply it to bare metal that has been cleaned and prepped with 80 grit to create scratches for adhesion. It is also fine to apply it over epoxy primed metal. The Evercoat's Rage polyester filler is for finer leveling of panels and is applied over epoxy primed panels.

Well-said, Lenny.

If you're going to do the work yourself, take the time to read and understand the products to get the best results out of them. Most complaints from people about body products is because they didn't use them properly or in the wrong application.