I was hoping you would repost in GENERAL but since not I will add this.
Sunchaser beat me to a bunch of it.
I agree you need to be really carefull with the lift capacity vs your stated expectation of 20K dry weight. A 20K dry weight boat, at least in my experience, will hold far more that 4K of supplies. Dry weight means no fuel or water and that alone in many boats is worth 2K or more. Water is ~8.5 #/gal, diesel is ~ 7.5#/gal.
Then you have to add all the food, gear, dishes, bedding, tools, dinghies, outboards and fuel and all the other STUFF we want, people that will normally be aboard. 4K # will be eaten up fast. Be carefull as many boats listed weights are optimistic.
I have only seen one BackCove here but nice looking boat so cannot comment.
I would also suggest
Camano, Nordic Tug, Ranger Tug, although they may not be for you.