I would have to say "older is better" when it comes to Commanders. It is true, they really didn't know how thick to make those hulls so they made them the same thickness as a wood plank, so the story goes. In many cases the Commander hull is easily 1" thick.
This makes a 38 Commander feel a lot heavier than the 35' wood Sea Skiff I had before owning the Commander, but the weight of the Commander is soon appreciated, as these hulls were designed to withstand 3X the stress of running FULL SPEED in a six foot sea.
The Corsair Division used the same gelcoat and resin, and same fiberglass, and to a degree the same construction techniques as the Commanders. Of course, CC would not put the same effort into a 17 or 20' boat as they would one of their iconic flagships, but the quality of the early boats is remarkably good. I have CC literature that overtly states the resin and gelcoats being used in the Corsair Division are the same as being used in the Commander Division. Owning one of each and doing all my own work over the years, I believe this to be absolutely true.
I have two 1966 fiberglass Chris Craft products, one is a 38' Commander Express, and the other is a Cortland built 20' fiberglass Sea Skiff. Would you believe the hull of that Skiff spent 25 years on Lake George, not real sure what happened to the boat during the other 17 years or so, but we found it up on Lake Ontario and the hull to this day has never been painted, still bare gelcoat, with no blisters.
In doing a total rebuild on the boat, I found the basic hull to be quite strong and stable, with some light weight techniques used to fix vinyl to the sides and flooring and all, but the glass part of the boat is as strong and good as the day it rolled out the doors of the plant.
The Lancers (and this Skiff) used a two piece hull, with the topsides being basically screwed or bolted down onto the bottom shell. This is an area where there can be some need for repair as the fasteners can shear if the boat is abused and flexes too much.
In 1970 the 38 Commander took on the Dick Avery aero look, and the cabin was widened to the edge of the boat and the outer walkway became an interior space. Chris Craft was beginning to realize their boats were over built at that time, but the quality really never dropped below the high standard, they just got a bit lighter.
Here is a small boat technique of fastening a wood nailer, so to speak, onto a glass hull.
HEre is the same type of hollow fiberglass box beam construction used on the Commander, but obviously on a much smaller structural problem to solve. They didn't do to well with those wood stringers, which on my skiff were updated with a better design that would not crack.
Here is the proof that the early boats are built heavier. This is a plug from the bottom of my 20' glass Skiff, built in Cortland under the same roof as the Lancers and small Commander 19 and 23' hulls. This plug came from the hull when I installed a new high speed transducer. Note the fact that the bottom is gelcoat, unpainted. Quality guys, quality!