The upgrade to the dinette area of our C&C27 was done originally to add more teak to the interior and to put sliding glass doors on the shelf-storage areas already there.
I found that the white table and the white wall the table was attached to was just a bit too much white for me.
Using the space behind the wall was a bonus.
We had no idea it was there until we removed the wall.

The upgrade is basically two pieces that fit together. The bottom piece is the wall that the table attaches to and the upper piece is a frame to cover in the shelf areas already there. It is possible to cut costs to make the bottom piece and simply cut out the door spaces in the old sheet of white covered plywood, or do like we did and buy a new sheet. You will need some new plywood to make the upper piece anyway. The upper piece is to mount the glass doors and opening doors for the shelf areas already there.

The first thing to do is with the table in place, decide where you want the new openings to be and mark them.
We made 4 new openings. One pair of openings, with no doors, finish off level with the in-place table. The shelf in each of those openings is about 3 inches below the table level. This allows for the items on those shelves to be held in place while under sail.
The distance between the 2 openings is governed by the width of the 110-volt ground fault outlet there. We keep coffee mugs and glasses in these two spaces. The other 2 storage areas are very close to the edges of the wall.
We marked for these 2 storage areas to be at about elbow level while seated.These two areas have doors that are bottom hinged and are held closed with magnetic catches. My wife keeps cereals in one and bread and muffins etc in the other.

Next, remove the table and the wall/ piece of plywood that the table is attached to. There are a series of screw nails holding it on, so it’s a simple procedure to get this off, revealing the useable space in behind.
Next you need to make the cut-outs you marked using the same sheet or a new sheet of plywood.
We bought teak veneer marine grade plywood to avoid any moisture problems down the road. It’s expensive, but worth it in the long run. We used our old wall as a size template and made the necessary cuts. Next place the wall back up and mark on the fibreglass hull where the new shelves should be.
They can be attached to the wood structures already in the wall, and painted. Again we used marine grade paint for this. We painted the hull area and the shelves a high gloss white to make it brighter in there.

Then a piece of solid teak was cut to fit on top of this wall unit. It was about an inch wide to accommodate the 2 tracks for the glass doors and went from end to end. A groove was routed out and a plastic track was pressed in.

The top piece was made from a piece of the same plywood. You will need to make a paper or cardboard template of the area so you can trace it on the plywood. No matter how careful you are when making this template, you’ll find yourself going in and out of the boat with the plywood making adjustments to get it to fit right.
By the way, we did this upgrade in the driveway near my father’s garage so as to be close to the tools needed. The top piece also has doors in both ends to enclose the 2 shelf areas already there. It hides the mess and can keep thing in place in heavy weather.

The size of the opening for the 2 storage areas cut into the wall (with the pull down door) is 14" wide by 5 ½" high. The actual space inside is 22" wide by 6 ½" deep by 13" high. Lots of usable space. Magnetic catches work extremely well.

The shelf areas with no doors (glasses and mug storage) are 13" wide by 6 ½" deep by 7" high. Very handy for things you need at the table. Note that the shelf the glasses are on is below the table level, but the opening is at table level. Note 110V outlet between the 2 openings.