Holy crap. That decoupler thing is genius. You not realize it, but the decoupler setup you have might be one of the best ways of dealing with booster stages crashing into the main rocket... Anyways, I've used FAR since 0.24, so I'm used to having to use fins. But I do avoid the static ones like the plague, because if you do a wrong maneuver, they make it a tremendous pain to correct it.