This is a 40"x50", 0.545-0.550" thick carbon fiber skinned honeycomb panel. It weighs 7.0 pounds. The gap between roller centers is 46.0".

Left photo shows no load, deflection 0.00".
 
   
 

47.2 pounds has been added to the center of the panel. Deflection is 0.19".
   
   
   

69.9 pounds has been added to the center of the panel. Deflection is 0.29".
   
   
   

101.7 pounds has been added to the center of the panel. Deflection is 0.41".
   
   
   

The last three photos appear to be exactly the same but they are not. The blue shape at the top is slightly different from one photo to the next.

This panel has the lowest number of skin layers per side that I would ever use. To stay within this general panel width, but increase stiffness, additional skin (laminate) layers can be added. Or if weight is the largest driving force and width is the open parameter, then a 1" thick honeycomb could be used instead of 1/2". Such a panel would greatly improve the above deflection numbers yet add very little to the weight of the part.