I played around with my mining PCs last night, and spent a good hour trying all sorts of settings on the single 280X machine. But I didn't change the TC, it has stayed at 8192, and the single 280X at 1100/1500 intensity 15 is getting 3.00 Mhash.
What different TCs are people using on 270X's and 280X's?
Pretty sure TC has no affect when using lasybears version.