There are a couple of utilities on the FunStuff pages that will allow you to alter the UV coordinates on an OBJ file. The ones I have tried are MapMagic and SuperMapper. I believe SuperMapper is listed as a UV mapper with multiple regions or something like that. I personally use the two of them together to create texture maps for objects I create. Hope that helps some .. . there are other utilities in Funstuff as well, but I haven't personally tried them, so I can't vouch for them. . . you might give them a go and see what you like.