UV trouble....

when you add your uv chequer map dont leave it on the standard setting increase the repeats across the u and v to say 10 or 15.

The reason for this is because at the size the uvs map is at the moment stretching becomes almost invisible at a per pixel level, so by adding the repetition on the map the number will become smaller and any stretching is more evident enabling you to adjust the uvs.

Now if all is well in the uv section but the stretching still occurs on the model in smooth poly mode, you can try adding loops here and there to strenghten the smooth at the borders but theres a little control that sometimes goes amiss within the attribute editor for the mesh...go to smooth mesh and drop down the list and go to extra controls, under the map borders its usually off by default just turn on smooth all....this can eliminate the issue most of the time.

as for suv, thats the first time Ive ever heard that one...just stick with your uvs from maya. The minute you have issues with uvs that come from zbrush you cant edit them properly in maya if you need to.

Ive attached a sample of it in action...its not a great example but you get the idea


Also with regard to zbrush pixels etc..the higher the res the better, thats for both mesh and texture....what you put in you get out


cheers
Jay