Changing texture size, how?

[Lyanastaader]

I'm working on a new model and everything is going fine, but I really want to change the 128x128 texture it currently uses to a 128x256 texture. I understand this can really only be done in VRS but, I'm still learning how to use VRS. I tinkered around for awhile, but nothing really worked. This is what I tried to do:

Selected the purple-shaded texture under the proper black heading in the schematic view
Selected "Texture Open"
Changed Y:128 to Y:256 and left X the same.
Saved the .dat file

I loaded model viewer and the texture was pretty messed up which was expected. I exported to 3dsMax to remap the model, saved the new .dds file, and then I exported back to MQO and loaded it into Model Viewer. The texture returned back to it original mapping, and texture.

What did I do wrong!?