You will lose the ability to store your pole on the mast..maybe a good idea..
But...would the conveninece of the radar be justified by having to store the spi pole on deck??
Besides, I belive the radar will wiggle with such small track support and move left to right, eventually breaking appart. The track cars need clearance to move, and hence the lose fitting you would get.
The radar would be above the deck light, so it would be well out of the way of the spi pole. By the way, I don't have a spi pole since I have an asym.
For permanent mount: Isn't there such a thing as "track stops" that get screwed tightly against the track? Either way, I'd make it so it would be very securely in place using tightened screws. And BTW, it could be an elongated mount with several of these tighteners and incorporate a triangular brace.
I know I could make a sliding mount that would not wiggle port and starboard.
Want to be my tester when I prototype this? You could lower it for racing and raise it for cruising!