1939 Ford Package Tray Question

[FatFndr]

I am trying to build the package tray for a 1939 Ford Coupe and have a reference 1940 Coupe for comparison. The wooden piece for 1940 Ford package tray fits in place nicely (it's an original). With the package tray installed, it is 1" short of covering the middle wooden piece and 2 7/8" short on each side. Since the reference car and my car are both in pieces, neither the owner nor I know what fills this gap. What information am I missing to complete this part of my build?