I'm still not satisfied with the stiffness of the brackets so I've decided to fabricate a Fore/Aft Strut to take load in the Fore/Aft direction. They will be made from 0.025 Al sheet and riveted to the rib and the Inboard and Outboard Brackets using 1/8" rivets. Images 1 and show my prototype strut mocked up in Cardstock. Image 3 is the final template in Cardstock.
Creating a Cardstock Template for a Fore/Aft Strut
Creating a Cardstock Template for a Fore/Aft Strut