Haven't tried that. Let me give it a go in a bit, but that kind of scares me. Yours lasts 15 minutes at 1.35 but mine can't go even go 5 at 1.325?
Just to test here, I loaded in at 4.5 GHz, just upping the multiplier and put it at 1.35V. It'll load up, run and all, but it hits 61 after just one...