Now have all my equipment stowed in Lowboard, the 3 small transmitter to the flap door from Lowboard - glued directly in front of the device. USB powered - optionally use a USB charger or USB port of any device. The receiver attached to the rear Lowboard that just sticks out of the head. Done.
It all works perfectly.
I can state from reach anything negative.
Seats about 4,20m from the transmitter. Operation is the same as before, when the devices were still standing on a sideboard.
Those who want to store no more than 3 devices in the cabinet -> buy recommendation!