Irish, the seat tutorial on cx500forum is a modern ergonomic seat that is supportive like many of the Corbin seats in many ways. So, with the lighter density foam you might be able to make it look one way when you are off the bike and feel like a contoured saddle when on it. If the vinyl or leather or whatever you cover it with is flexible enough to let the light foam on top expand to the brat style when off the seat but feel like a contoured saddle to fit your anatomy when riding to make it very comfortable and support. I have not seen this done, just a hair brained idea if it could. Talk to a couple upholstery shops to see if they feel it would be possible to do. If it does not hold up then it is going to be sagging and look bad. The light foam would have to be accounted for when it is compressed almost completely when you are sitting on it. There are multiple densities of foam from high density to light density. As well as chemical composition. It will have to be a foam that will stand up to heat, instead of an interior foam for a seat in your house.
David