Unable to set bed size (M211)

[dylanmc]

I've got a Printrbot Simple Metal with extended bed (10"x6") & heater.
I flashed RevFv1.0_Printrbot_Simple_Metal_HB.hex

Connecting to it, I see the dimensions are the default 6"x6" - no surprise.
So I tried to set it with the M211 command, but it reports the default:

M211 X254.0 Y154.0 Z152.0
echo:Soft endstops: On   Min: X0.00 Y-2.00 Z0.00  Max: X152.00 Y152.00 Z152.00

Am I missing something?
[Edit: this seems to be a duplicate of Bug #7 - which is closed, but I'm not sure what I'm supposed to do. The release notes for the current version which closed the bug talk about being able to set "build volume" but I don't see how to do that, or if that's what fixes it]