---

Hi SD
Ive been away awhile...sorry for the delayed response.
For the two aft corners, I cut some drain pieces from Starboard. I am fortunate to have a CNC machine so I drew a computer file that appealed to me and cut it out on the machine. I have simply placed them in the aft corners without sealant or fasteners such that I can lift them out to pull the drain plugs, clean or service those areas easily. I will try to remember to take a photo and post it for you in the future.
As far as the transducer is concerned, I mounted it on the Whaler Drive. Since I have twin outboards, I mounted it between the motors, 4" towards port of the centre line. I was worried about getting a clean flow of water there because of the step between the transom and the Whaler Drive. I used an Airmar transducer and am pleased with the results. The Whaler Drive complicates the flow of clean water and I was close to glassing in a through hull option. In hindsight, I'm glad I didn't.