No chance Nick with the door jett handles they are really blocked and you cant get to them if the seat is fitted in reverse.
HC Dukane DK 100 was 38 KHz and about 30 Nm range for a hand held hydro-phone. Smaller beacon now.
Sorry N, not an expert in sonar but it will suffer the same problems as radar, false reflections. we used to call it bounce.
Close to rocks etc.
The 92 windows in the middle cabin are VERY tight
Not easy to get a passive sonar boat into Sumb head. I know you worked that out.