93 SN carpet and upholstery renovation

As you guys can see..my in floor "cooler" lid is pretty much shot. the piano hinge is rusted away, as are all of the fasteners, and the two little pieces of wood that stiffen the hinge area are shot as well. I am thinking of cutting a piece of marine grade plywood, and just making a solid cover. However,  I need to think of what thickness to use. Once carpeted, I don't want it too thick or too thin.   Should I got with 1/2" ply, or 3/4" ply?   Thoughts? 

So my question before I cut and start to lay my new carpet, does the black trim/channel that goes all the way along the sides of the boat get glued down first, and then you cut and tuck the carpet into that trim channel?  Or do you cut carpet to outer walls first, then fit the trim channel onto the carpet, and then glue it down? 

on my 93 that carpet doesn't go under the gas tank, there is a finish strip much like the sides of the boat in front of the gas tank. So carpet will get tucked into that.  For the metal engine frame I cut the carpet right up to the edge, and cleaned the edge up so no old carpet is sticking out..then will glue the new carpet right up to that edge.  

Nice work Dan

Well, she's all back together. New upholstery, new carpet, a good wash, wax and buff and she looks good as new. 

Some more pics......