Being a Northerner I loathe waste, and therefore avoid cutting at all cost. Accordingly we shall leave the buoyant sections of our flat-catamaran hulls all-square (rectangular actually) and instead use a rail along which the swinging-arm can be guided, as here.
I am veering toward the pusher propeller for three reasons beside its thrust-line:
Firstly, and this is where our experience building large drones comes in, the arm should be as rigid as possible when fixed in the horizontal. This is when the boat will be hovering (for the first time since the ride of the Valkyries) and reliant on electronic equipment that is susceptible to vibration.
Secondly it has a nice 'action' because unlocking it from this position it will swing into the hovering position under its own weight, and nice and gently because of that short lever-arm.
Thirdly, conventional marine practise requires a pusher propeller and though there are a few out there, tractor propellers ~ and we are talking water-screws here ~ are rare. I think this is because the 'hub drag' would be greater.
Aircraft too go faster with rear-mounted propellers, but they have never been popular in the air because they are less stable than tractor types.
If you're not convinced, try pushing a supermarket trolley around with a stick and then pulling it instead with a piece of string, and see how far you get.
It'll probably get you confined to a nursing home, where you'll ace flight stability.
