Not familiar with the interior, but is there a large vacant area near the converter? I had a nice area on my 228, just above the detector, water pump and water heater switch, where I mounted my Trimetric battery meter, and the remote display for my PI EMS/Surge protector.
There would have been plenty of room to mount a small radio / CD and the nice part is right behind was the converter, so taping into a 12V circuit would be very easy. Either through a possible empty fused circuit in the converter, or into another 12 volt circuit using an inline fuse to the radio.
The wood is nothing more than very thin paneling. So in my case, I cut the holes for the Trimetric and PI display for the wires, and then where the mounting screws went into the wood to hold the units, I placed 1x1 pieces of wood on the inside. That way the mounted screws went through the thin panel (which would not hold anything) and into the 1x1 wood and clamped the 1x1 to the backside of the panel.
Trailer: Lifted 228BH, heavy duty springs and Yokohama tires
TV: 2016 GMC Sierra Z71 4x4 CC, SLT
Spare TV: Two Alaskan Malamutes
Living somewhere in ID; previously lived in Moab UT; previous to that, don't ask!