RE: Transmitter trays
Always use a tray. Home-made.
I have a hook on the near edge of the tray, which tucks behind my trouser' belt. Keeps the tray exactly where it's meant to be, whether I'm flying 2.4 or 35 meg.
The only problem with the hook is that, now, I can't go model flying in the niff ... no belt, you see.