It needs its own UV space within the 0-1 area-- not stacked. So some shifting around of other UV elements/islands would have to be done to fit it in there. Even if the UVs are identical, if the texture needs to be unique it can't be stacked.
Hi everyone! quick question, Im pretty new to MUDBOX and i would like to Isolate Or Mask a whole part of my object while im painting, A little bit like the SELECT ELEMENT in 3ds max. is it possible?