Here is the deck light from Marinebeam, had it installed today it fits just fine.
On the subject of the led lights in the cabin I have reposed under (6" recessed lights). the modifications I did.
Attached our the pic of the deck light and the switch and dimmer switch for the main cabin lights. If you pull the old dimmer out you will find the wire for the main cabin lights behind it. I just put the Blue Sea dimmer behind the switches. The 12 volt constant hot to the CFL lights was for a constant voltage for the ballasts that were built into the lights. Just pick either hot leg and run it to the new dimmer. You only need the dimmer hot and ground wire to make them work. The on off switch is on the right in the photo. It supplies power to the dimmer. The switch that in the middle is the dim switch it is wire to the dimmer (wiring instructions come with the Blue Sea dimmer). The switch on the left is the red courtesy lights.