This is what the installation instructions say:
this horn should be mounted so that the cylinder is vertical (with the horn facing down). There should be no more than a 15 degree variance from the vertical position. If it is not mounted per these specifications, then the horn may cease to function after a period of time.
instructions found here http://www.bikerhiway.com/installinfo/Stebel/stebelhorn.pdf.
If you aren't having any problems then that opens up more possibilities for where I can install the horn. Thanks.