RE: ideas for radio tray
Trace around the TX
Draw the desired total tray shape around the TX outline. Cut from 1/4 ply. Make a cradle unde the TX. Attach your neck strap to the tray.
Neck strap can be like a long purse strap... and be flexible. Or you can make up from strip aluminum stock for a stiff style (bend the shoulder curves.... pad with foam of some sort...
It desn't have to be fancy... it just has to work.