Nicko,
Assuming it can be mounted correctly it is technically possible. The bigger question is how much performance loss will be incurrred. Below is a screen shot from a vessel that had an in-hull installation where I compared the signal loss. One suggestion would be to take some screen shots of the sounders performance with its current ducer setup. Then remove the ducer, put it in a plastic bag of water and set it in the bilge. Take the vessel back out to the same area and take another set of pictures so you can compare the two installations.
Snips