Welding Tips and Tricks

Trying to add side rails to my Jeep. The rails are 3/16"
Been trying to weld to body sheet metal.
I have an old inductor Marquette A/C box (pick current by moving the lead position to a different hole).
I have tried 6013 3/32, 1/8 7018 1/8 at different current settings, rod angle etc. Seems to melt the sheet metal no matter what I do.
It is held in place due to the ends have thicker metal to weld to but would really like to make it airtight as this will keep out future corrosion from road salt.
I have some 1/16 7018 on order and can get 1/16 6013 locally but last time I tried it always stuck.
Any ideas?

For flat welding I ran a large puddle of 7018 at 100 amps and short arc and pushed the puddle into the sheet metal with ok success but was left with the large puddle to grind flat (its the step). I even tried some brazing rod but the arc still melted the sheet metal as the braze puddle froze too fast if I kept the arc away from the sheet metal .

Zjtins.

Thin auto body sheet metal to be welded to a thicker 3/16" rails, and you want to do it with stick.

Not much experience myself with thin stuff, butt I would not give up on the 1/16" 6013.
The joint needs to be tight, squeezed together to eliminate any space between the cleaned surfaces.
You might not have access to the back side of the sheet metal, but if you do, place a bar of metal to push the sheet towards the rail, that will help close the space but also help with heat absorption.
The electrode needs to be more oriented towards the rail which is thicker.
Those skinny little rods move around like a whip, so I'd use the free hand to guide the electrode as close as possible to the end of the rod.
You may only be able to weld a series of stop-and-start tacks placed upon one another.

Probably some of the WT&T members with auto body experience will blow my approach to ell and back again, but I would give it a try ... finding that minimal amps needed to make the rod run.

Let me know if my advice ends up worthless.
Alexa