As long as your tails are placed well for your sail and the draught of the sail is within a range of efficiency this is generally what happens: If the leeward tail is stable(ish), and the windward tail flicks around, you bear away or sheet in. If the windward tail is stable(ish) and the leeward tail flicks around you come up or sheet out. However, there are situations where the choice is one side or the other. In which case I recommend you chose the leeward side to keep stable. As wind velocity increases, the likelihood of you consciously having the time to think about what the tails are doing reduces dramatically. Sail trim becomes a balancing act ("of feel") between weather helm and boat trim. The only quick indicator you have to avoid capsize is the leech tail, which will give you a rough idea of how far away stall/overpowering is. However, once you master the feel of the boat under heavy conditions, even those become defunct.