I posted this pre-hack, but I thought I'd post it again for anyone looking for ideas about how to permanently mount a stereo without taking up valuable storage or cutting holes.
I used a boating stereo cabinet, a Poly-Planar WC-70 that comes with a surface mounting bracket.
Click to view attachment
Got some surface-mount 120 watt speakers with enclosures and mounted the entire setup under the cabinet below the rear dinette.
The antenna installation was the most challenging, and I found a Tune Trapper TT2C internal mount hidden antenna that mounts inside the cabinets and required no drilling through the hull. It really works!
Click to view attachment
Here is one source for the antenna; I bought mine from a vendor on eBay.
Tune Trapper antenna source
Roger