Vacuum forming- plastic thickness help???

How flemsey/strong is the thinnest sheet of plastic that can be used for vacuum forming? I want alot of detail to come out, but I don't want to worry too much about reinforcement if I don't have to.

Thanks

If you are using ABS you can use 2.5mm for good detail versus strength. If you use the same thickness of HIPS (High Impact Styrene) I have found you can get a little more detail but you give up a little strength.

I think the big question would be how often do you plan on wearing whatever you are making and how much of a beating are you going to give the costume?

The depth of the detail will matter as well. If you have a deep pull it will thin out the plastic quite a bit in the valley and high spot.