My only comment would be that the back tank perhaps leaves you standing further forward in the boat than you really want to be. If you’re kneeling on the back tank you’re in a less efficient stance. (Standing on the back tank doesn’t bear thinking about). Good question though. Anyone?
It fits on the top of the transom, offset from the centre, beside the cut-out in transom for tiller. It’s the only experience I’ve had of sculling but works ok as far as I can tell. Certainly handy for coming alongside compared with having an oar sticking out the side as in rowing.