pic: FTC290 2011-2012 Mast

[Chris is me]

I wouldn't be too worried about the stability, as long as you don't move with the mast extended.

Good strategy.

[BJC]

I don't think it would be too hard to attach some passive stablizers which flip out when the arm extends up. That would probably help a lot if your concerned with tipping and don't plan to move after raising the arm.

Very Cool, this is the highest I have seen a robot extend so far.