looking good man. Regarding your piano hinges and concealing them.....
There are two ways of installing them (parallel or perpindicular) to the decks. I have seen guys do both here. If they are installed perpindicular (standing up), you will only see the hinged part of the hinge. If you do it parallel (flat on the decks), you see the entire hinge.
If you are to install them perpindicular, you should take some consideration into the screw holding ability into the side of plywood. bassboy (on a rare wood build) modded a boat where he used lumber around the edges of his hatches for improved (an needed IMO) screw holding. It required some guling, buiscuiting, clamping etc... to make it happen this way. Not sure the thickness of plywood you used, but it's certainly an option to simply screw in the hinge this way without the additional lumber, just knowing that the hatches would need some extra consideration in how they are used if you wanted them to last. I've also seen guys do that on here, but can't remember off hand who, to ask how they are holding up.
For the guys who lay them parallel, I've seen folks cover all but the pivot part of the hinge with carpet, some dado out the thickness of the hinge from the plywood so the hinge lays flat (level) with the plywood, some don't, and some simply attach the hinge on top of the carpet. I don't know that any are right or wrong, but simply personal preference.
If you scour the builds, you should see an example of just about every possible hinge configuration.