Also depends on the finished product, I do a lot on 100% poly and have bold white lettering on top and bottom of a 11 x 14 design 3" tall letters white on a dark grey shirt. Design also has green and red in it, but point is, with an underbase and to make the white kick out the finished product feels like a huge plastic decal on their back. Did a wet on wet doing the white last with a fill and push stroke and the white comes out bright enough and the hand is soft and is more desirable. This is a military unit and they use the shirts for PT etc and really like the results. Also makes my printing go a lot faster with no flashing etc as well. Look at the whole job and look to offer options to your customers when you can, you may be surprised and it helps you. Good luck