In my many years experience of doing game conversions, I've found that it is a complete waste of time to try to save a decal. It will stretch, crack, fall apart, etc. Usually they are brittle and the slightest attempt at removal and they are destroyed. That's why many manufacturers sell brand new replacement decals & graphics. Many older games now have people making reproduction graphics & decals. It's better just to remove the old decals, throw them away, and buy new ones.