TOPIC: Floor rebuild in 1970 Glasspar CATALINA G3

Hi All
I just took possession of a 1970 G3 that is in need of a floor and stringer restoration.
I started to take out the foam bits and fiberglass and wood pieces that were still there, most of the wood had turned to dust. After I pulled out the foam between the stringer and chine I noticed that the hull flexes when you push on it with your hand. This is my first boat restoration doing a floor and stringers and am wondering if this is common in the Catalina G3 hull. Is the bottom flexible without the inner foam and wood to support it. This hull also looks very different in its construction from the older G3 that I see on the website, dose anyone have any experience with this newer G3 construction.
Any help would be greatly appreciated
WJK