Instrument panel questions

[RS]

I am wondering if 1/4" is thick enough to support all gauges, radio and fish finder/gps? Or should I go to 1/2"?

The problem with Starboard (or Seaboard) in the length you need will expand and contract quite a bit (about 1/32 inch per linear foot over a 40 degree change). The contractions in the winter will cause the corners to crack where fastened(been there, done that). I suggest some 1/4 inch plexiglass. It is more rigid and thermally more stable.