hovercraft raycast and automated ground obstacle-avoidance

An few years ago i put here an post how to make an hovercraft like wipeout etc…

I found one o made that apen, but still no get it how to…
I try to made the same as it show in the video, but i give up:(
http://www.burgzergarcade.com/demo/technical-demo-anti-gravitational-suspension-system

Anti-gravitational Suspension System.

i try many ways , by using ground obstacle-avoidance and few raycasting no looky:( give up.

Any adea or axamples??
My head burn, i don´t wana burn my head again:)

Sorry for this open this new post.
http://unity3dextra.49.forumer.com/viewforum.php?f=2

What kind of obstacle avoidance are you looking for? If you want the vehicle to go up and down slopes but drift over small bumps as though they weren’t there, then it’s just a matter of using the forces correctly. Generally, a hovercraft script is set to keep the object a set distance above the ground. This involves measuring the distance to ground (usually with a raycast) and then applying a force at the position of the ray if it is too close to the ground. Effectively, this is like having the craft pushed away from the ground on a spring. Using a weak force for the spring will tend to give the effect of letting the craft pass smoothly over small obstacles while still being able to go up and down slopes without too much trouble. If you find the craft crashes into slopes that are too steep (or else collides with the ground after falling heavily) then try using more raycasts and force points.

just need craft avoidance ground, track, thats it, the rest is up to me. If any one have any good point of view to made it, share it please.
And the RayCast , i´m not familiar whit RayCats, sence its an little confuse for me!! I see many engine that Raycast works diferent ways!?