I remember the Dumas Diamond as a kit that was obsolete and sold at discount by AHC when I got into big (35 size) flying.
Back in the day, it was common to use simple 1/2" x 3/8" hardwood mounts all alone. As with Riley Woote's Voodoo, it was soon realized that the hardwood needs some help from plywood or a balsa pod.
In 1959, Fox Stunt 35's, McCoys, and such plain bearing engines were used in combat. I think a Diamond would do better with a modern 25.