Originally Posted by due ruote

I was totally speaking from my own perspective. If you want to try it, go for it. To my eyes it looks like a big challenge, especially if it’s going to be ridden. If it’s just for display that’s a different matter.
Re the rails, sure they are straight, but pretty rusty, which for me would just be one more reason to find another saddle.
I have had pretty limited success with epoxy on plastic, even when the package says it’s for plastic. And if it’s being ridden, it’s undergoing all sorts of minor torsion pretty much constantly, so you would really need a good bond.
As for the foam, I have found it pretty hard to match the density and firmness of saddle foam, and certainly getting a seamless transition won’t be easy.
Again, not trying to talk you out of trying, just offering some observations that would lead me in a different route. YMMV.