Yeah 7075 is pretty hard to bend. Try to make a curve rather than a corner- 1/2" diameter is the smallest curve I'd recommend for material that thick, 3/4" to be safe. Otherwise, like MM said, it might crack.
Edit: Actually I just went back through the thread and saw that it is 4mm thick ( I had thought it was 3mm), so definitely >3/4" diameter to avoid cracking.
