Hi, Kingfarm. It's lovely to meet you at last! Offering moral support definitely counts; if I hadn't been there, my DH wouldn't have dared tinker with our crawl space.
Is the floor over the crawl space a single layer? or two layers? although I'm not completely sure what difference it makes as far as smells.
I get "old house cellar" smell from my floor registers, but in the room with the single layer of floorboards, which is over a crawl space, there's no smell, just cold floorboards. (We've since laid another floor in there.)
My cellar and crawl space also are adjacent, and I recommend screening the opening to the crawl space so that animals cannot tunnel into the crawl space and then hoppity-hop their furry little hides into the cellar. We don't have a neat opening like that, so we couldn't do that.
It would take so much work to make our cellar into useable space that we just decided not to bother. It is still useful for storing rocks, plastic lawn chairs and glass canning jars, though.
maybe if you just sprinkled about a quarter ton of baking soda on top of the visqueen.....