I haven't been able to find my original pics you asked about, but these might give you a better idea of the DB in the cassette:
You can see the cutting board layers which were shaped to fit the cassette. The shape for the DB was copied from the Adventure DB slot. The layers were bolted together to get the final DB holder. This was then bolted into the cassette and an aluminium sheet, shaped like the cassette was added underneath the cassette for a base for the bolts to go through. Eyebolts were added fore/aft as well as a cut down miragedrive axle for the locating pins. The cassette was then filled with a mix of lead shot and tile grout to add ballast.
As RR pointed out it worked well in the front drivewell of our old Oasis when we had two sails. If used with a single sail the best position was the rear drivewell.
A bonus with the DB, apart from stopping sideways drift when going upwind, is that it adds stability when sailing. With the DB in the down position, heeling is slowed noticeably, and you have more time to adjust the sheet in strong gusts. I always sail with the DB down when out in my AI in kayak mode (small sail but no outriggers ).