Hi David, I have tested dye sub on 50/50's. It has a faded vintage look. The reason obviously is that the ink is ony adhering to the 50% polyester of the shirt. It does adhere to the cotton but gets washed out or fades fairly quickly after a few washes. But for a quick vintage look it is not all that bad. If it designed properly with some distressed scratches and such and use those new distressed T's it might be a big seller.
Who sells those? brand specific? or am I not searching for the right thing. You can pm me if you like.