Set video settings to default low. Exit game. Then reload and adjust to your liking. I went from 10 fps on ultra. to 30 fps. BUT !!! The next day i had to repeat this process. Still not a bad workaround. I am running a 4th gen i7 with 16 gb of mem, with gtx nvidia 760 water cooled, and a samsung ssd 850 pro.
I run ultra full screen, with grass off and high detailed landscape on. All other settings are the default ultra settings.
I have been told and i tested that fullscreen does seem to give more fps.
Long live the Silverleaf Clan