If you have it completely covered up, I think it would be pretty hard to have it completely dessicated. I'm finding that all the ones I have with a plastic cover over them are hardly getting any leaf burn while the mosos in the wind with no protection are getting close to top-killed depite only breaking the 10F mark twice. If you are willing to keep it wind-protected every winter no matter how big it gets, I think 3 inches by 40ft should be possible.One Moso also had a surprising number of undamaged leaves. I'm going to keep a close eye on this one.
Today it reached 48F and the snow is almost completely melted so I can have a good look at my bamboos.
I've found that the worst performers so far are Bambusa vulgaris-top killed, F Robusta-nearly 100% leaf burn P-Henon mostly leaf burned and P-Vivax(regular green kind). They might get hardy enough to over-winter after next year, or they might keep dying back and stay small, but they shouldn't be a first pick for a zone 6 bamboo grower.
Everything else in the garden seems to be holding its green pretty well.
The bamboos that had little to no damage here are:
F Rufa
P Atrovaginata
P Aureosulcata(yellow groove)
P Bissetii
P Parvifolia
P Rubromarginata
Other than the Bissetii, all of these bamboos were planted in 2009 and they are already showing exceptional hardiness. Lets hope the weather stays fairly warm for the next 7 weeks.