Rust Preventive Coating for Top side of Floor Pan?

I am renovating my '68 Beetle but hoping to not have to remove the body from the pan. I am fortunate that there is only light rust on the floor pan as I cleaned it down and painted it probably 20 or more years ago. I need to choose between something like Rust Bullet or POR 15 as opposed to cold gal paint (much easier). I expect I will be able to remove most of the existing paint but not all as I am not able to sandblast without removing the body. Any constructive suggestions appreciated. Cheers..........Wayne

I would not put POR 15 on if the body isnt coming off.

Just use something like White Knight Rust Guard

Hi, I use this stuff that I get from Mitre 10. Its also good on tinware, bumper brackets etc

Might be a very late an answer, but I use KBS Rust Seal (an aussie product, better than POR) on my pan. It's as hard as nails and can be applied with a brush.

Also out of curiosity the pan on my '68 is a very dark grey and not black. Many in the SAMBA argue that pans only ever came in black, but my family owned since new is not black.

Here's the completed hand brushed result of the whole floor pan.

Thanks viiking. After changing my mind a number of times and asking advice from my local VW resto workshop (who recommended POR15) I am now waiting on delivery of a Rust Bullet kit. Rust Bullet, POR15 and KBS all appear to be very similar.
As to the colour, I am unsure because this is the second time in the car's life that it has had the paint changed on the floor. I can say however that the tunnel (which is original) is definitely black. On the other hand, the original seat frames and gearshift were definitely dark grey. My '68 is a German build. No idea whether that has any bearing on the pan colour though. Your pan looks really good done with the KBS
Cheers