plenty of threads about where others have mounted their WS-420 here, not all specific to your boat but should give you some ideas! What's your dash looking like, any area to install under the dash?
I was having a difficult time determining where to install mine (I have a Supreme V226), and ordered a 12x24" sheet of 1/4" thick ABS plastic
for $25 and will be cutting a 6" wide piece to run under my dash the full length, will seal/glue/screw into place using some of the under-dash fiberglass to attach to, then mounting the WS-420 to that using the stock brackets. Still waiting on the ABS to get delivered, should have some pics to share soon!
You can also check out (as you can see, I've been researching the install process too!):