Ok, so you made me go out and start some measurements! lol.
Based on the manual, flush mounted with 11 degree angle from center of dome, I am fully clearing on the sides, just barely since my hardtop curves to the sides and some also toward the rear and forward. Interesting design on the hardtop, never realized how much is curves.
Since the radar is mounted forward with a lean forward, it allows the beam to clear aft as well, but just barely.
I can watch my prop wash when running, so that tells me it is doing pretty good!
I think though, the 25 degree part of the beam, is where I lose some from sides and rear, rear not being that important but as I approach a marker bouy it will disappear when starting to pass when it is about 30' or so away whereas back when I had my 3G and was on a mount, it would see it nearly right next to the boat.
Due to my clearance issue, I am happy with the results so far.
Would I use a mount and get some elevation? Sure, but that is just not an option for me. I had quite a few tree scrapes on my 3G even with the canvas cover on it I use when travelling.
One of these days, I dread hitting a branch hard enough to crack or break the radar!