Yepper, 4 REOs going at 6v right now.
One with a 3.5Ω 510 (Grand)
Three with 3Ω Boge Cartos (Woodvils)
I can't seem to go back anymore. I used to be able to switch back and forth but I just kept going with the 6v more and more.
A couple days ago I took my grand at 3.7 with me for 9 hours and it was pretty disappointing compared to what I'm used to now. I won't make that mistake again.
Sad thing is I just bought 50 2Ω cartos 2 weeks ago. Guess they will sit and wait for my VV Woodvil so I can crank them up a bit.