Fixing rust holes in the floor

[Spartan]

I am going to get a Q of POR 15 (black I am guessing) to do the floor of the Charger.   I have a nickle to quarter sizes rust hole on both the driver and passenger floor boards.  What is the best and most permant way to plug them.  I see POR 15 has a couple products for it.  The floor is in really good shape other then these 2 holes.  Once I fix the holes and use the POR 15, do I need to paint the floor with my green car color to make it original?  I saw the reinforcement in the back seat are has a popped weld, my dad said not to worry about it but knowing it is busted drives me nuts.  I want to fix it but sinse the car is not here I don't have access to a welder.  Do I need to worry about starting a fire if I have a guys mig weld it in the back seat area?

Thanks for the help.

Sparty

[Drop Top]

The best way to fix a rust hole is always the same. Weld in a patch. If you take out the carpet and seat there will be less chance of starting a fire. If you looking for originality then you need to mist in overspray to most of the interior area. Leaving primer exposed around the driveline hump area. Most people (me included) go ahead and cover the entire area. I use just the base coat and I don't clear over it.

[69hemi]

Drop Top is right as always that the only way to stop rust is to cut it out and weld in some new metal.  The object is not to get the metal too hot when welding so just use short tacks and the threat of fire is reduced.  As far as painting goes I like the solid underbody look but the fogged look is correct so I went that way.  Either one works it is just up to you. 

[Spartan]

RIght now the entire interior is out of the car since I am replacing all the carpet, upolstry and repainting the seat springs.  I don't have access to a welder or I would do what you are saying.  I probably will when I get the body redone but that is a year or two away.  My 1st order of business was to get it road worthy starting with rebuilding the engine last fall.  Sinse the interior was the next bad part of the car, I am trying to get that done.  Body work and a new paint job will be the final fix.  The trunk floor is pretty ripe with the leaky back window.  I will probably pull the headliner to see what I have under the roof sinse I have a vinyl top on the outside.