In my testing on the SPECapc lightwave render tests my chip can do:

451 seconds @ 4.8GHz max temp 71c
431 seconds @ 5.0GHz max temp 76c

5 percent gain for 5c ? I don't think it's worth it. 71c should get better this weekend tho, going under water.

This magical 5GHz number is making usually rational people insane.