Was fun to test it.. was going by .2 degree increments, even 66.2 on my monitor (16x9 atm) started drawing models further out from the edges as very close, seemingly sucking the distant parts closer to the center along with it. There seemed to be no point going smaller...
Yeah i agree around 70 the cockpits look great, exactly what you'd expect if you were sitting in the chair. Literally everything else drawn on the screen is broken though unless you're looking straight down the middle ?
IMO with FoV set to 70 the fisheye effect is already there, but still very minimal, I end up not even noticing it unless I'm specifically looking for it. For instance if I stare at the edges of the screen while going through a station mail slot there is a slight "stretching", or in screenshots with planets near the edges of the view point may look a bit egg-shaped.