Wide angles lens gives you more flexibility than you think. With our GoPro, we've had good luck either just aft of the bridle on the spin pole (under the jib), or on a small sprit extended out in front of the spin tack. Both locations give you a view of crew and boat on both tacks.

You would think that foreground items like the mast (or spin tack block) would dominate the view, but with the wide angle, they kinda disappear.

Edit - forgot the last sentence in your original post about being accessible while sailing. While the sprit idea is out, with a bit of dexterity, I think the under-jib position is doable.