HY-SR04 mechanical mounting

I printed up a mount that I thought would improve receiver sensitivity, but it appears the fixture is "ringing" with every ping and the max measured distance is suddenly 6 cm. Before inserting the sensor in the mount, it appeared to be working great, up to 235 cm. I assume the fixture is "ringing" because if I squeeze the cone tight with my fingers, the ranging starts working again. So I put caulk all around the cone to "quiet" it, but that didn't work at all.

Anyone got an idea for a mechanical fixture for this ultrasonic sensor?

You see some examples here but these will not improve the range of the sensor (as far as I can see)
http://www.banggood.com/search/ultrasonic-sensor.html

Try putting hot glue around the bottom of the mount and that will stop the ringing and should make the range go back to normal. But I don't see how it would improve the range.