I mount two long antennas on opposite sides of my canopy. Use a block with Velcro to keep the antenna tips clear of the canopy. Having transmit on both antennas as with Fusion is even better.

Unfortunately Flarm advertised dual transmit with the Core 1.1, but omitted to obtain approvals for North America.

For a new glider I'd spec Flarm and transponder antennas in the fin, perhaps with an access panel, and the secondary Flarm Antenna on a canopy side to cover the blind spot overhead the tailplane.