I'd say your best bet is to put Belt Left on the walls to the Right, and Belt Right to the walls on the Left. Like this.


BRÂ(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)BL
BRÂ(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)BL
BRÂ(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)Â(-)BL
BRÂ(-)Â(-)BilsyÂ(-)BL
-------------

Not sure how well it will turn out, but I guess you can get the idea. It works best if the belts are at a high speed, because otherwise you'll see him sliding off the walls.

Yes, I HAVE tried this, it DOES work.