F550 and Maxbotix MB1242

Is anyone out there flying a F550 with a Maxbotix MB1242 or similar?

I am, and while ground tests show the sensor to be working, in flight things are not so good. My sensor is located near one edge of the F550 bottom plate. I suspect that prop wash may be keeping it from working.

If you are flying one of these sensors and have it working, how did you mount it?