HS/Elevator Enclosed Ends - Question

I am building a 7 but liked the method for enclosing the ends used by Vern Little.
The photo looks like it has a lengthwise stiffener.

Does anyone have more details on how this is made and material thicknesses?



Edit: Silly me -the answer was right in front of me. A fresh look in the morning - found the picture of the stiffener. Still not sure of the material, but 025 is still looking good.

Bump - Close

I had the information all along. Vern had posted a picture with the plate in it, and I missed it while focusing on the stand offs. It has been added to the OP.

Note that the two photos are of different parts of the airplane. The first photo is the end of the horizontal stab, the second is the inside of the end of the elevator. The standoffs mounted in the second photo don't match the screw locations in the first photo. You can see how Vern mounted his lead balance weights as well, using hex-headed bolts that screw into nutplates on the rib.