A better way to check for noclip is raycasting down from the player and checking if the object is solid (CanCollide on)
I recommend only kicking the player if they are in the middle of the solid object or are making their way through one because sometimes players are able to stick their hands or legs through solid objects:
This is a great tutorial on explaining how to make good anti-cheats for you game I highly recommend checking it out: A Guide to Making Proper Anti-Exploits