Can I use POR15 on the bottom of my floorpans to prevent rusting? Theres that undercoat thats on there from the factory so I'm wondering if that will interfere?

 

I dont see why not. Just make sure they are cleaned and degreased verywell.
I used the flat black on my rear when I did thr 4thgen rear swap worked great. I am actually still trying to get a few drops off of my hands [wear rubber gloves at all times, even opening the can] If I were you I would contact restromotive ind before buying the paint just too make sure it will work with your aplication. por-15 is expensive...

 

i did it to my car and its well worth it. my firebird is lookin good but my sister 91 camaro lookslike u can almost punc tough the floor pans causeofall the rusting DO IT!

 

I used it on the entire bottom of my car as well as on my suspension parts. The only thing I would suggest is getting their metal ready solution to help etch the metal otherwise the paint will have a tendency to peel off in certain smooth areas.
The stuff works great. It's strong and definately prevents rust. I used it on my IROC and my father and I used it on his old Datsun and we all know how those POS recycled beer cans like to rust out!!

 

I had my two starter kits bought in the spring with plans to do that this summer, but I never got around to it.

Maybe next year, and maybe next year I'll finish polishing my rims.