I have designed a small tunnel entrance for the Litter Robot that is about 18 inches long. It is made out of black corrugated plastic drainage pipe that is 12 inches in diameter. I'm not sure where you can get this stuff, but construction crews use it when building new neighborhoods (thats how I got a piece).
The tunnel is mounted to a weighted, wide base stand. The stand allows the tunnel to basically butt up very close to the entrance, but not interfere with the rotation.
The cat comes out of the unit and enters the tunnel to exit, and litter that is flung (is that a word?....lol) out or stuck in paws drops into the deep corrugations in the pipe before the cat exits.
The biggest problem was weighting the wood frame stand, and for that I just used a plywood box built into the base of the stand, and about 10 pounds worth of concrete.
The tunnel itself has two wing nut/bolts on the bottom that I use to securely mount to the stand. I can easily remove it to dump the litter in the toilet.
All told, iit took me about an hour and a half to build, not including the varnishing. Now I will get to see if it actually works......lol

