walking below ground

when i have a ground with two planes (A/B) below each other, ralph (roaming-ralph-sample) is always on the higher one (A)/ can’t walk through it being always on the lower one (B):

-> how do i have to built the mesh/ how do i have to script it, so that ralph can walk below (A) AND down through (B) the “bridge”? thx

Lower the collision ray’s origin, around the knees is good. Its height in roaming ralph sample used to be too high among the clouds.