Imo, you should always use a mount for the radar. The larger the top, (T-top/hard top area) the higher the mount, so the radar's beam clears everything.
I've always mounted satalite receivers, (gps, XM weather, Serius, etc) below the radar's path, either on the shortest stantion type mount, or surface mount, (puck). That way, there's no risk of breaking the radars beam. I prefer the short stantion to surface mount, because I believe it will "see" a satalite that's low, on the horizon, better than a surface mounted one. In either case though, I've never had a problem. Also, I think the further away from the radome or array, the better the "view".