VR Character Z coordinte variation problem

I have the following VR_Character:
21-07-2016 03-17-19 p.m..png
The scenario is that the character starts in one mountain, and he walk forward untill the risk . The character must fall down but it just fly.
I have Gravity activated, collisions, and if i change the PlayerStart to the border of the risk, it falls like it suppost to do.

After some other test, the Z value of the character is related to the HTC Vive Camera so if i walk in real life trough a planar surface, in the game i must walk like that, this is good. But if the floor ends like at the border of the mountain risk, the character must fall. How i achieve this?

Found some work around.
Control the Z coordinate of ActorWorldLocation trough BluePrint. Cast a line trace downwards the actor position (take acount of rotations) and handle the location vector of result hit. Like that u should have the Z coordinate given the floor setoff