Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
Overall light strokes are much more effective than heavy or the long ones.
You can hit mountains, but not ones with spikes.
Keep in mind that the balloon can handle about four minor hits before it explodes.