floor pan patches--butt or lap weld

[69Tom]

OK guys, was wondering your opinion on this, as I've seen it done instructionally and by people on the web both ways.

My car is not going to be a show car--it's a driver. I will keep it as nice as I can, and original as I can. I am not undergoing a frame off restoration. I am fixing what I can when I can on it as a driver.

First off, I have a front driver's floor pan to patch. It's incredible I have to replace it, as the rest of the floor pans in the car look as if they're day 1 from the factory, as does the rubber mat. I guess water/salt from the driver's boots would get trapped under there each winter and it took it's toll. That's the only explanation as there's no leaks anywhere.

So, question is, should I lap weld the patch or butt weld it? I know I'd like it if it were butt welded and then ground down. However, I'm always worried about getting a close enough fit on the existing pan to the replacement patch. Plus my access to the underside of the car won't be incredible. I don't have a lift....

If there any downside to the lap weld? Is it frowned upon?

thanks.