I do not know the angle, but I have had the lee rail under water on a number of occasions - very exciting, but not the most efficient way to sail. By most accounts the boat is fastest when sailed flat, or with just a touch of heel.
I have yet to capsize, though my experience has been that easing the sails (if you can) is better than heading up as the aft end has little freeboard and tends to dig in and take on some extra water when rounding up with that much heel. Of course, that could speak more to my heavy hand on the tiller when she goes vertical than it does to any characteristic of the boat.

Tiller extension is definitely a plus if you plan on testing the limits of heel.