Mine is mounted on the back stay about 10 feet up. I am also considering moving it to the mast but it works so far where it is. 

Mine is mounted between my two back stays (non standard setup).

Some points on location.

1.)  Your heel angle can be more than 15 deg for some time (a tilting dome is a very very nice feature "I used an old turnbuckle to adjust the tilt on my setup")
2.)  Height may be required in waves above X high ( mine is at about 15' above the water it has issues in 20' + waves, and 20' waves hide all the small stuff)
3.)  be aware if it will shade any solar panels
4.)  The higher it is the more g force it will receive (shorter life, well at least a tougher life)

5.) MAKE SURE IT WILL NOT MICROWAVE YOU, OUR YOUR CREW!!!!  remember radar was how the microwave was invented! (look at the brodcast angle and make sure a 6'+ guy is not in its way while on deck)

I found the swing out (in to the companion way) for the display works well (I have a lexan weather board so it can be used in heavy weather and be well protected)

Hope this helps you find the right spot.
Norm