Looks very clean to me. I have mine mounted to the same place on the other side, but I don't have any rubber - it's mounted solidly. I used both bolt holes.
The manufacturer's physical mounting instructions include this: "This transducer must be suspended between flexable hoses on the inlet and exiting ports. The hoses must be supported within 6 inches of the transducer."
Most installations I've seen here show a physical mounting of the cube. The strange thing about the advice they give is, if the cube is not supposed to be mounted, why did they include 2 mounting bolt holes? Perhaps over time they have learned that solidly mounting the transducer where there is vibration reduces the service life of the transducer.
I've seen a lot of installations using adel clamps, which also provides some dampening of the vibrations. I guess if mine quits and I have to replace it, I'll re-install a new one with some kind of rubber mount to reduce vibration transfer to the transducer.