Well, as far as I remember a narrow FOV could lead to another problem, and is motion sickness. I remember to suffer this problem playing Turok 2, ten years ago - I couldn't play it for more than 30 minutes (I wasn't the only one). I began to feel nausea, a very very bad feeling, and soon realized by myself that the problem was caused by a 45º angle or so. That happened to me also playing Half Life 1, but it was the only game that I've ever played for so many hours per day... (something like 8-10 hours, but after that I physically couldn't afford keep playing). May Outerra engine will not probably be oriented to an 'action packed first person shooter' style, but, IMHO, I think you should take account of this problem too. Anyway, 60ºh should be enough, although I will always welcome to a slider with that option.