Epoxied transducer 1 foot forward of the transom and it works a treat. Put it onto the flattest ( most horizontal ) hull area to minimise any dead space twixt hull and transducer.
No loss of sensitivity and now it doesn't flick up like it does on the transom after a few hours of use, which used to cause a mis-read. Not an inaccuracy as it was giving the correct reading for it's angle, just that it was reading away from the boat and not straight down.
So this works. And well.