No, you shouldn't have to. What you describe is the method I use to add scars and tats to Michael textures. All you need to do is apply the revised texture to skinbody or skinhead depending on where the scars/tats are. Try saving the revised texture as a .jpg file rather than a .psd file Every once in awhile a .psd file can be so big that poser doesn't seem to load it properly - though admittedly that just usally just tends to make my copy of Poser crash when I try to render rather than render the wrong texture.

"Do not meddle in the affairs of cats, for they are subtle and will piss on your computer." -- Bruce Graham