hi.
Never try the blow torch myself, but I heard that the carbon smoke from it may discolor the acrylic. In addition, if not done properly, the acrylic may become more plastic, and flow down like a lava. Or even worst, start to burn. Acrylic is very flammable. Either way, you will end up with a bigger mess than a scratched one.
Hydrogen torch won't have the smoke problem, and I heard that's what the tank manufacturers use. Note that H2 torch is much hotter than propane...
bye -ck-