The Maxwell architecture can handle 1.3v just fine. 1.312 is getting up there pretty good....I wouldn't suggest running that high. Most of them are limited in the stock bios files to run at 1.275v or lower, so unless you modify your bios, or hard mod your card, you won't be able to run higher than that.
Avac, you need to look again, man....screenshots. 1.37 on air? It'd be cooking inside the case.