If you want to support my efforts please consider donating at: paypal.me/RobSMods2021

Installation:

Backup your patch_english.dat and patch_english.fat first
Unzip the file into C:\Ubisoft\Watch Dogs Legion\data_win64\
Update the folder location above with the directory where the game is installed
Click overwrite if prompted. 
This will replace the pre-existing 
patch_english.dat and patch_english.fat files
The DLC language files will be replaced by updating these files.
To activate ray tracing parameters you need to select the 'Ultra' preset from the Ray Tracing option in Video/Graphics settings in game each time you open the game.


This mod updates the Ultra Ray Tracing preset on PC to use the E3 demo parameters. These settings have been extracted from the patch.dat file which includes a folder path:
> engine > settings > defaultrenderconfig.xml
Replaces the 'Ultra' quality raytracing effect with the E3 demo version. This directly affects the ray length (distance of visibility in reflections) and the ray length decay.
Original PC highest preset:
        <quality id="pc_4"
                 Enable="1"
                 QualityLevelIndex="3"
                 RoughnessThreshold0="0.075"
                 RoughnessThreshold1="1.0"
                 UseCompressedFormat="1"
                 StaticInstancesBvhRadius="192"
                 DynamicInstancesBvhRadius="32"
                 ClustersBvhRadius="192"
                 BuildingsBvhRadius="192"
                 TerrainBvhRadius="192"
                 RoadsBvhRadius="192"
                 VegetationBvhRadius="192"
                 ParticlesBvhRadius="32"
                 BoundingRadiusThreshold="0.25"
                 EnableWaterTiles="1"
                 EnableParticles="1"
                 EnableProjectedDecals="1"
                 LitterAndGrassRadiusRatio="0.25"
                 AlphaTestedGrassRadiusRatio="0.4"
                 GrassDensity="0.6"
                 RoadDecalsSizeThreshold="1.3"
                 DecalsAllowAnyNbrQuadsOfQuads="0"
                 RoadDecalsMaxNbrQuads="4"
                 DisableTeethGeom="1"
                 AngularSizeThreshold="2.0"
                 LightMaxNeighborCellCount="4"
                 MaxProcessedLightCountPerFrame="2048"
                 DenoiserType="2"
                 CheckerboardMode="2"
                 NrdEnableBicubicFiltering="1"
                 RayLengthMin="2.0"
                 RayLengthMax="192.0"
                 RayLengthDecay="8.0"
                 SSRStepRate="2"
                 SSRMaxSteps="256"
E3 Raytracing
         <quality id="e3_marketing"
                 Enable="1"
                 QualityLevelIndex="3"
                 RoughnessThreshold0="0.075"
                 RoughnessThreshold1="1.0"
                 UseCompressedFormat="1"
                 StaticInstancesBvhRadius="288"
                 DynamicInstancesBvhRadius="32"
                 ClustersBvhRadius="288"
                 BuildingsBvhRadius="288"
                 TerrainBvhRadius="288"
                 RoadsBvhRadius="288"
                 VegetationBvhRadius="288"
                 ParticlesBvhRadius="32"
                 BoundingRadiusThreshold="0.25"
                 EnableWaterTiles="1"
                 EnableParticles="1"
                 EnableProjectedDecals="1"
                 LitterAndGrassRadiusRatio="0.25"
                 AlphaTestedGrassRadiusRatio="0.4"
                 GrassDensity="0.6"
                 RoadDecalsSizeThreshold="1.3"
                 DecalsAllowAnyNbrQuadsOfQuads="0"
                 RoadDecalsMaxNbrQuads="4"
                 DisableTeethGeom="1"
                 AngularSizeThreshold="2.0"
                 LightMaxNeighborCellCount="4"
                 MaxProcessedLightCountPerFrame="2048"
                 DenoiserType="2"
                 CheckerboardMode="2"
                 NrdEnableBicubicFiltering="1"
                 RayLengthMin="2.0"
                 RayLengthMax="288.0"
                 RayLengthDecay="8.0"
                 SSRStepRate="2"

This file replaces a separate smaller patch file: patch_english.dat & patch_english.fat - the reason for this is because these files are significantly smaller than the main patch file which has grown considerably since release and includes all new patches since the games release.
Why add the E3 ray tracing settings?
The E3 demo used higher ray tracing settings than the current Ultra preset available on PC, in theory if your GPU is powerful enough you're able to go beyond Ultra. 
If you want to support my efforts please consider donating at: paypal.me/RobSMods2021

Thanks go to digital foundry for covering the original settings across the consoles. This galvanised me to attempt this mod in the first place.
Additional thanks go to the members of XeNTax game research forum for the tools as well as advise from the members including but not limited to:
superdemus
Combragamer
And final thanks go to the tool creator: rootCBR 
https://github.com/rootCBR