This is what I use for fuel proofing, http://www.minwax.com/wood-products/...g-polyurethane , The firewall, engine bay, wing saddles, fuse bottoms any where fuel might get to. I use it to fuel proof the wood before I cover the plane and have never had a problem. This stuff soaks into the wood and is thin and much nicer to work with than epoxy. However.... I've never used it on top of a fabric covering.

So okay, your thinking.... how does this fit my situation??? Well....I don't see why you couldn't use it over covering its just that I've never done it. It is fuel proof though. The only thing I might worry about is that it might yellow over time after exposure to sunlight. But as your covering is cream and black you might not notice it (or it'll give your plane an old timey fabric look). The other thing I might worry about is being sure you got all the old chemicals off before putting this stuff on. Did the Polycrylic soak into the fibers or underlying wood??? good luck getting it out. My gut tells me that your probably going to run into contamination problems but its worth a try before pulling the covering off.

I did notice these products that "might" not have the coloring problem but I have no idea how fuel proof they are.

http://www.minwax.com/wood-products/...d-polyurethane
http://www.minwax.com/wood-products/...ane-for-floors

My mother swore by spar varnish and I'll admit its tough as nails but everyone I've used really yellows over time. This stuff has a UV blocker though... Hmmm, may have to pick some up and try it myself.
http://www.minwax.com/wood-products/...-spar-urethane

Hope this helps,
Mike