The Re-Released Kyosho Optima Mid is designed to take a modern brushless motor. However, the modern ESCs that power them are also taller with the addition of a cooling fan. In the Manual, Kyosho state that you can adapt the upper deck with a small cutaway so that modern ESCs can be mounted in the intended place on the lower deck. Even with the adaption of the upper deck, the installation is still awkward, and leaves the ESC vulnerable as shown below.
This mount uses the two existing holes in the chassis designed for Kyosho’s own ESC. Using 2 4mm CSK M3 screws (supplied), the mount fixes flush to the chassis to provide a flat platform so that the ESC can be fixed more securely into place.
Designed by rcnand available on thingiverse: https://www.thingiverse.com/thing:5793585