Given the susceptibility to water damage of the factory OSB / particle board subfloors of most FGRVs, I have three words of advice:
Pick up a nice , high quality vinyl remnant from a flooring shop, cut it to shape - make a template out of paper or cardboard, - lay it down and voila, you have a great moisture barrier that's easy to clean and protects that water sensitive subfloor.
I gave our sub floor a heavy coat of oil based paint
to seal it and then laid a thick, self padded vinyl remnant over it. We've been pleased with the results. The only area I glued down was at the entrance. We do keep a small throw rug on the floor, especially in cold weather. The nice part is that when the rug gets really soiled, we just replace it with a new one.
I do like the Pergo and we would have gone with a sheet of it if we could have found a remnant.