Removable Through Hull Transducer

[Waterborn]

I am looking at installing a Through Hull Transducer in my boat. I was looking through the archives and found several suggestions on placing the unit in petroleum jelly/ KY etc. to test it out first. I am wondering if anyone has done this as a permanent install, so it would be easily removeable. (easier than grinding thickened epoxy) I would isolate the area somehow to protect the vaseline (or whatever) and the unit from water, contamination or damge. Does anyone see any problems with this idea? Also, I hope to be able to install the unit well behind the keel dead center of the hull.

Another concern I have is it would be in between two intake screens (plastic I think) that are 7.5" apart and hang below the hull about 1.25". If the unit (which I have not purchased yet) is, lets say 3.5" diameter, then would the screens interfere with a 20 degree cone being only 2" away?(again they only stick out the bottom 1.25")
I guess I am wondering does the beam (cone) start at a pinpiont or does it start at the full width of the tranducer? (I am leaning toward a Lowrance HDS5 system)

Thanks for reading!