Yes I have tried doing that a little using MSI afterburner but my preferred OS is a Linux distro so I would have to flash all of their BIOS I guess right?

Is that what you did? It's always made me nervous really, but I have wondered about the "stilt" BIOS many times. Unfortunately I have many different kinds of 290s - only 3 of them are reference versions so if I went down the rabbit hole of BIOS modding I think it would take me a lot of reading and learning (and risk of bricking cards).

Another issue is that I mostly run them with core overclocked (1100) and memory underclocked (1125) so undervolting is going to complicate that too right?