Thanks in advance to those of you with superior welding skills.

By way of brief history, I have a six-cylinder conversion with front mounted oil cooler and Puller fans. I'm going to build sheet metal ducting to exhaust the hot air out through the bottom of the trunk.

I have already mounted the fans and the cooler and in the process of determining how to exhaust the hot air.

I purchased two louvered panels with the intention of cutting out a section of my front trunk and installing these panels to help exhaust the hot air coming off the front oil cooler. I know there are several different methods to attach these including lap welding and butt welding but I'm not sure the best way to do this for a good finish on the sheet metal and the welds. I want to avoid water getting trapped and rusting the trunk floor.

Here are some pictures of the trunk and the new panels:





I'm sure a butt weld with stitch welds around the perimeter would certainly seal it but I wonder how nicely the underside would look and how hard it would be to finish the underside.

I have a flanging tool so I could create a slight flange on the louvered panels and cut the opening slightly smaller than the louvered panels so they could set on the step.

I suppose I could also plug weld them and use seam sealer on the inside. I just wonder how well this would waterproof the bottom side.

I also bought some weld through primer which I have never used. if I decide to plug weld would this be a good opportunity to use this? If so, any clues on the best way to apply this product?

Again, I appreciate any input on this since my welding skills are very novice at best. Thanks guys.

Personally, i would butt-weld them and grind both sides flush to make it look like one piece of metal.
A bit more work, but worth it IMHO.

Oh, and one more thing, the raised portion of the louvers should be on the underside of the car, in the air flow, to help with the exit of the hot air.

Way easier to flange and spot weld those in but the risk is greater for rust than if you butt weld them and grind both sides. With proper care lap welding works just fine. There are lap welds all over the car. Weld through primer, good seam sealer and paint will likely be enough for long term rust prevention. are you installing the louvers up or down... Something doesn't look right there.

Yeah, I figured as much. I just layed them in for effect.