Fuel Tank sub floor replacement

[EagleOCNJ]

What I am actually trying to figure out is if the floor piece under the plywood should be set in place so it sits equally on the beveled edges of it (on the hull curve) and on the center / keel stringer. The olde piece does have a light imprint down the center of it from the stringer.

It actually looks to me like it was not secured to it but sat only a slight distance above it. I was considering just epoxying a strip down the keel stringer to make it connect to the tanks floor so it doesnt bounce around.

Sorry Im not getting it but its real important for me to understand before I move forward.