Blu, I'm planning a sawdust unit for Pit Stop. Rick and I found plans in The Cloudburst books by Vic Marks.
Rick has made MANY sawdust pit outhouses too--a hint if theres any odor, put about a 1 oz scoop of agricultural lime in, works great and helps speed decomposition.
I am amazed at the amount of room that little bus has, plenty of room for a "privy in the corner" behind a screen. Also means I'll have to put curtains on that corner too.
In the book Reuses, there is a way to make a urinal from a bleach bottle and a hose you could run into your sawdust box too if you want a unisex bathroom

Lois