I was curious to see whether performance in FC4 would improve using FC3 settings, seeing as its the same engine just with a few additional settings like fur etc. So I replaced the gamerprofile.xml from FC3 and dropped it into the FC4 folder equivalent. Low and behold I got superior performance, and this is with my settings in FC3 set at ultra. It also fixed the mouse acceleration issue.
The downside is the FC3 profile doesn't have the extra settings like fur, trees, etc. So I decided to create my own hybrid gamerprofile.xml. Seems to work well. I get additional performance and its not placebo.
here are my settings:
PHP:
<GamerProfile>
<SoundProfile MusicEnabled="1" MasterVolume="100" Language="english" />
<ProfileSpecificGameProfile Sensitivity="1" MouseAcceleration="1" MouseAccelerationOn="0" MouseInvert_y="0" MouseInvert_y_Flying="0" MouseLookSensitivity="4.17232" Invert_x="0" Invert_y="0" Invert_y_Flying="1" Swap_Triggers="0" Flip_Triggers="0" InvertSticks="0" DefaultFlickFireDirection_y="0" ControllerLayoutVehicle="0" ControllerLayoutBuzzer="0" UseMouseSmooth="0" Smoothness="1" Smoothness_Ironsight="1" HelpCrosshair="0" Gamepad_vibration="1" UseRoadSignHilight="1" SubtitlesLanguage="invalid_language" TaggingEnabled="0" WikiUpdatedEnabled="1" CollectibleUpdatedEnabled="0" TutorialUpdatedEnabled="0" ObjectiveReminderEnabled="0" CraftingTipsEnabled="0" DisplayXPEnabled="0" DetectionIndicatorEnabled="0" HitIndicatorEnabled="0" ExplosiveIndicatorEnabled="1" MapIndicatorEnabled="0" HealthIndicatorEnabled="0" CrouchIndicatorEnabled="0" KarmaIndicatorEnabled="0" AmmoIndicatorEnabled="0" MinimapOpacity="3" LootReadoutEnabled="0" CoopPartnerIndicatorEnabled="0" UseAmbx="0" GamepadFeedbackLayout="0" Autosave="1" Machete="0" DrivingAssistEnabled="0" DifficultyLevel="1" IronsightToggleMode="1" ShowPVPTips="0" ShowPVPTimer="0" ShowPVPScorebar="0" ShowPVPPlayerTags="0" ShowPVPObituaryMessages="0" ShowPVPNotifications="0" ShowPVPMasterVoiceToggle="0" ShowPVPFactionPowerUpIcons="0" ShowPVPPlayerNames="0" PlayPVPIntroVideo="0" HasVisitedCoopMenu="0" SelectedLanguage="english" Coop_Friends_Only="0" DrivingAutoAimEnabled="1">
<FireConfig QualitySetting="VeryHigh" />
<CompressedClasses />
<Statistics>
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
<Stat Value="0" />
</Statistics>
</ProfileSpecificGameProfile>
<RenderProfile AntiAliasingMode="0" MSAALevel="2" UseTrippleBuffering="1" VSyncMode="1" UseMotionBlur="1" SDSM="1" SSAOLevel="2" EnableNvidiaPCSS="1" GodRaysLevel="1" FurLevel="1" TreeTessellationLevel="1" Version="1" AlphaToCoverage="1" ResolutionX="1920" ResolutionY="1080" Quality="ultrahigh" QualityEditor="editor_ps3" Fullscreen="1" Borderless="0" UseD3D11="1" D3D11MultithreadedRendering="1" WidescreenLetterbox="0" UseWidescreenFOV="1" FOVScaleFactor="0.997408" AspectRatio="4" VSync="0" VSyncWindow="0" RefreshRate="0" DisableLoadingMip0="0" GPUMaxBufferedFrames="1" ShowFPS="1" Brightness="1" Contrast="1" CalibrationScreensShown="0" GammaRamp="1" AllowAsynchShaderLoading="1" SafeFrameAreaWidth="0.85" SafeFrameAreaHeight="0.85">
<CustomQuality>
<quality ResolutionX="1920" ResolutionY="1080" OtherQuality="high" EnvironmentQuality="high" AntiPortalQuality="high" PortalQuality="high" PostFxQuality="high" TextureQuality="high" WaterQuality="high" DepthPassQuality="high" VegetationQuality="high" TerrainQuality="high" GeometryQuality="high" LightingQuality="high" ShadowQuality="high" ShadowCinematicQuality="high" EditorQuality="default" Hdr="1" HdrFP32="1" ReflectionHdr="1" EnableVertexBinding="1" id="custom" />
</CustomQuality>
</RenderProfile>
<NetworkProfile VoiceChatEnabled="1" CustomMapMaxUploadRateInBitsOnline="10240000" OnlineEnginePort="9000" OnlineServicePort="9001" FileTransferHostPort="9002" FileTransferClientPort="9003" LanHostBroadcastPort="9004" LanClientBroadcastPort="9005" ScanFreePorts="1" ScanPortRange="1000" ScanPortStart="9000" SessionProvider="" MaxUploadInbpsOnline="10240000">
<Accounts />
</NetworkProfile>
<GameProfile />
<RealTreeProfile Quality="Ultra" />
<EngineProfile>
<PhysicConfig QualitySetting="VeryHigh" />
<QcConfig GatherFPS="1" GatherAICnt="1" GatherDialogs="0" IsQcTester="0" />
<InputConfig />
<ZoneConfig />
</EngineProfile>
</GamerProfile>
if you set the gamerprofile to read only after tweaking, the game will crash if you attempt to change settings. So best to get the way you want before thinking of doing that.