I installed a C-Head composting toilet last week, and this last weekend we had the chance to use it while on a short 3 day trip.
Installation was pretty straight forward, remove the previous head, build a "mating" plate, and a grate. The pipe connecting to the black tank includes a flange that protrudes up about 1/2" from the platform floor, and as the C-Head requires a flat surface, I built a plate that covers the bottom of the C-Head with a hole cut-out for the flange. I did not connect the C-Head to the black tank (it's an option to route the pee into the tank which we'll consider later), and as our pod is new and the tank clean, I just left it un-sealed.
The C-Head sits a little higher, so I constructed a cedar grate (with walnut dowels) to fit in the shower pan. It makes sitting on the head more comfortable, esp. for my 5'4" wife and 7 year old, though it does make it a little more awkward for me at 5' 11", as my head hits the ceiling standing up... still not to bad. I remove the grate for showering.
Nothing complicated with the install. I ordered the optional hold-down straps and those, along with the round cut-out for the flange, make it pretty secure.
Worked great over the weekend. Smells like peat moss. I was wondering if there would be any pee smell, and there was none. I've read some people spray a little vinegar water down in the pee trap to keep it smelling good, we'll probably do the same... but for our short initial test, no odor at all.
We emptied the pee jug before taking off in the morning. If we stayed put somewhere, we'd probably be emptying it every day, maybe stretch to two days depending on usage. I didn't find it inconvenient, and we can always route it to the black tank later. Poo still sitting in the head, will empty it out this week. I don't expect any surprises there. Still smells like peat moss.
So far we're really happy with the unit. Our goal is to get at least a week's work of usage before having to empty the "compost", and only have to deal with pumping the grey tank.