The night owl is definitely longer and wider than the Hennessy, so it'll be easier to lay flat (as illustrated in the pics on the WL site). I have a HH Deep Jungle XL and it has the same dimensions as your Explorer Deluxe. I've never experienced any calf pressure in it but I'm only 5'9". One thing to also consider is whether your feet are too low. This can cause your lower legs to be constrained as your body settles closer to the foot end. Make sure the head end is at least 6" lower than the foot end.
Anyway, if it's comfort you're looking for you should be able to find it by getting something a little bigger than the Hennessy. Have some fun and make one yourself. And don't get caught up too much in hammock religion.