I have the right side floor pan, the right & left side rear seat pans installed. I lap welded them from the top and ground down the weld. The question is what do I do underneath? Should I weld the seam closed underneath also or seam seal it?

Thanks

I would weld that seem for extra strength, either fully or spaced lap welds.

i welded mine in top and bottom and im planning on seam sealing both top and bottom dont want any chance of any rust forming in the weld
good luck