So last year had the GTX345R installed in my Acclaim S.   With 4 people and bags the signal was there but unusable in the pilots seat.   Solution: GTX345 has a single vent hole which is also, per Garmin, where the Bluetooth signal escapes the fully shielded LRU box.  A sticker on the unit states to install with the vent hole on top.  However, other Garmin instructions indicate installation with the vent hole on top or bottom is acceptable.  My unit was installed by Hartsell Avioni