Yeah, I’ve tired and failed to make an IK feet system in the past and that’s why I’m using ALS (Advanced Locomotion System) for this project, the whole player capsule moves based on the root which the feet determine as the player moves up and down terrain - it’s not a smooth transition unfortunately.
Well that’s it though, the hand, body and all jump as the foot IK moves the legs up to the new pelvis position in a jagged way. This is why I was thinking of a Feet IK offset to the Hand effector a while ago. But perhaps you’re right that fundamentally I went in a wrong direction of blueprinting this - I was so **** close too 
I’ll try a trace as you’ve suggested and do away with the spline completely (the rail was made externally to UE4). Perhaps I’ll upload a video of what I got so far.
Thanks for your hep M8.