CustomPhysicalProperties Friction set to 0 yet it's STILL decelerating?

I am trying to make a landslide type thing where the blocks have a NoCollisionConstraint with the smooth terrain and they slide down a ramp which is inside the terrain, so the blocks slightly stick up through the terrain... I have set the friction of the ramp and the blocks to 0 yet it STILL decelerates?? Do they perhaps have friction with the terrain?

Edit: Actually I just tested moving the ramp and the blocks ABOVE the terrain and yes, that is the issue... they have friction with the terrain which they are not able to collide with.. any solution to this?