What about just another layer of foil on top? Would that not help?
Possibly. Yes. If the putty sticks I could apply it to the existing layer and, once it's dry, I could apply another.
I am not making a very accurate model, like JohnnyTodds Yokosuka. It it is more like a impressionist piece. Or dadaist, if you like. But still, I want it too look about right. There are a bit of confusion between versions of the Victoria (and the Vernon, Valentia) different engines, angle of the wing, style of rudder. I don't bother much about that, though.