Quote - "Most of the MAT files nowadays won't work in P4 anyway" 

Haven't found one that doesn't - P4 simply ignores what it doesn't understand. Also, AFAIK, good luck getting Daz Studio to take an unaltered .mc6/.mt5 file. MAT files may be old but they are the universal format thal all the applications understand. If it's for yourself or you want to limit your target audience, the newer ones are fine.

Given the number of complaints I see about using MAT files in D!S I would say they don't work very well. I haven't run Poser4 since P5 SR2 came out so I can't check but I would imagine that trying to load a MAT files with the texture burried some 20 or so nodes back in the tree would result in nothing being applied to the figure.

For maximum consumer happiness I would say a seperate D!S mat would be in order. If you already have a DS mat you might as well go ahead and switch to MC6.