I killed both of my Montana goats out of the same willow tree by a pond. The willows were only as big as your leg and I got up about 8-10 feet with a Windwalker hang on - it was kind of hinky when the wind blew, but I had some limbs around me. I had does walk right under me, and talked to them a couple times...they'd look around, but not up. Never got busted. 14 hours in a Windwalker treestand is a LOOONNNGGG time, though!
I did some sitting on a fence crossing with a 10 ft tripod I packed way back in too...that was another story. They picked me right off. Of course there wasnt a tree within a mile of that stand so no cover. The guys I talked to about tripods generally backed them into some kind of low tree or bush cover around a pond.
From my (limited) experience 10 feet is plenty high for goats....if there is some other cover to help blend into.
Ryan
Here's buck #2 - not the biggest goat in the world, but I was tickled with him on a DIY type hunt.