DayZ Object detail option

[HellionXC 0]

hey guys I've got a rather weir issue with the dayz graphic settings, first off my PC specs;

Nvidia GTX680 (4gb) in SLI (not that it matters) 
i7 3930 at 4.7ghz
16gb ram

http://i.imgur.com/fd3TMWx.png

these are my settings basicly.. however.. when I change objects detail (it changes the amount of grass on the floor my fps plummets to oblivion.. I can actually only play on low/very low or normal. i've seen people with less performance running on objects detail very high. I'm quite clueless on how this happening.. anyone got an idea?

[fully 51]

Simular specs as you, average 50-60 fps.
Lastest drivers..etc windows 8

Whats different to your!
Vis=1600

ATOC = disabled

Terrain Detail = Very High

Object Detail = Very low - easier to find loot from chopper crashes =)
Shadow detail = High - this can kill fps some times

HDR quality = Very High

PPAA = FXAA(Sharp filter) - High

Interface size = Normal