Peter,
The receiver module is an integrated module, it is the orange portion of the picture RJ provided. The antenna referred to in the manual that needs to be above the PCB is just the portion of the integrated module that RJ has out above his green PCB. He doesn't have the entire wireless module overhanging the PCB, just the antenna. The green PCB is basically a daughter board that can be plugged into the Lynx Express. It does overhang the top of the LE PCB, but only to get the mounting correct, the needed components on the daughter board and the ground plane configured on the daughter board per Microchips specifications. I don't see how it could be any smaller.
Also, the way the LEs are mounted in their recommended enclosures the antennas should be vertical.
Hope that helps.
Ron
***woops RJ beat me to it***