Probably my q9psv, that has worst dissipation. I notice it hotter than my old broken q9. My old q9 was stable at 1,8, but my q9psv has some unstabilities at 1,8 GHz, so i guess it's my new.device. difference between 1,6 and 1,8 is very minimal though, so not a big deal.
I use it at 1'6 and it's stable, but i cannot claim that all devices allow 1,8. So those flashing it a 1'8 GHz do it at your own risk.