inhull

Hi All, I'm looking at adding fish finder/bottom contour information to my GPS - I'm really after bottom composition and contour more than fish, and this requires addition of a 50/200Khz transducer. There are many flavors available, and the one Garmin has for in-hull use e.g. don't cut a hole...

I want to install an in-hull transducer on my Ericson 23 II. Is the hull solid fiberglass or cored? I have never drilled a hole in the hull, so I don't know. Where is the best location for placement of the transducer? Any other advice for epoxying the transducer in place? Thanks, Fred Nelson...