I have a triple denim, a double denim, and a cheap blast shirt. I used them this way last week: Cheap blast-500x3, triple denim cut back-550x3, double denim no cut-580x3. None of these reps actually touched my chest they all lacked more or less an inch. I even pulled on some of them. I am not strong enough for your friends idea. The most I have ever touch and go'ed is 630. I am sure if I used a super tight shirt to cut it would take more than I can lock out to get it down. However, our definitions of super tight could be very different.
Soc.