Replying to Tree Slides help?

My snowboarder compadre who's pretty much the only person I ride with often has started sliding on laid-over trees.
I've tried to follow him a couple times by riding onto it with just one ski and the other ski on the side of the tree, tip up.

The problem is is that I always seem to fall off the side with my foot hanging before I want to. If I can even keep my other foot balanced to begin with and don't get knocked to the side.

Any tips? I've ridden on logs where they're much wider and can fit both skis (it's just like going straight over a box pretty much) but something about just 1 ski on a smaller tree just doesn't work in my head.