Seacraft Hull Construction & mounting transducer

[RS]

Another option is to glue (5200, 4200, epoxy, marine-tex, etc) a starboard or acrylic plate to the appropriate region on the transom, and screw the transducer to that. No holes in the transom that way

Don't do that with starboard or seaboard. It does not bond well with 5200 et al. The result might be that the assembly comes loose at 40 mph and swings up into the cockpit killing someone. Also, the cable should be mechanically fastened to the transom for all transducers so that if the bracket breaks, there is not enough reach to swing into the cockpit.