Photoshop :: Getting Rid Of Partial Transparency And/or Forcing PS Not To Use It?

offering dark t-shirts that allow transparent PNG's to be used. Unfortunately, the printing process for dark shirts leaves white wherever partial transparency is present, which usually leaves a white halo around images and text.

Is there any way to force PS to not use partial transparency? Partial transparency looks great on white shirts, because the different printing process sees it as another form of white. It would be great to be able to toggle between usage and nonusage of partial transparency.

You can save for web in PNG-8 mode which dithers the partial transparency areas, but it also drops the color count down to a level that makes the design look bad. So far, that's the only way I can see to remove the partial transparency from already finished designs.