Disable CharacterMotor But Detect Grounded?

I want to allow my character to climb an arbitrary mesh, this works fine atm by disabling the character motor and allowing movement along the y-axis to move them up/down.

The problem is, i have some cases where the mesh sits below ground, and my code will then allow the character to climb "down" far enough to fall through the ground.

I know there are solutions like checking distance from ground, etc... but what I'd like to do here is to use the charactermotor isgrounded (or charactercontroller, but that appears just updated via charactermotor anyhow).

So question: How do I disable input/gravity on the charactermotor to allow free movement instead of just disabling charactermotor so I'm able to use isgrounded?