There is normally not enough room under the seat and the transceivers we have seen under the seats have been noisy due to interference caused from the bike.
The 3101's also are slightly bigger and run a longer more flexible aerial which fitted under the seat can cause aerial bounce where the aerial in touching the frame causing broken comms.
Running the Kenwoods away from the seats will give a clearer sound quality and also improve the distances between the bikes.
Rich