DwayneSpeer is correct. In my defense, in Step#1 where I indicate that a taper is to be made, Dwayne's suggestion is what I was getting at but did not adequately describe. I didn't have an exact ratio in mind, either 12:1 or 15:1 but something along those lines. Either way, it's easy to draw a 4.5" "target" circle and grind to the circle.
I really don't think that roving is that hard to wet. Using gloves, dip it into a tray or similar container with epoxy until wet. I suggested roving because it is stronger and builds quickly.
I wouldn't leave the transducer in place. I did that on our last boat and it was a mistake. The o rings will eventaully dry out and a leak is waiting to happen. Much better to do the job right and debate these details, IMHO.
Thanks guys, for the suggestions. This is what makes Sailnet great. I was not aware of the ratios even though I've done this job and other similar jobs in boatyards and my own boats for nearly 30 years. We always made a taper, but not to a specified ratio. In retrospect, we were pretty close but relied on eyeballing it.
Thanks.... learned something new again.