For the litter scatter, I have tried the fence and the ramp. I found the
ramp really effective as my boy used to leap out (in joy Im sure) and trail
litter like a comet tail. The ramp encourages a stately waltz down the steps
which are angled to catch litter from paws, before getting to ground. A mat at
the end of the ramp completes capture in most cases, and certainly improves
tracking hugely. 

Shadow is a digger, not a flicker. If your kitties are flickers, then a
fence is helpful. 

PS accessory price includes shipping with Australia Post Australia wide ;o)