So I have UL-19. I'm looking to do some some changes that I'm hoping that help. I do have some questions.

I'm starting with eletricronics tray. It weights 10.1oz


I have a friend that cutting me a smaller 1 piece tray out of carbon fiber.

I was thinking using 2mm thickness, would that be thick enough or should I go to 3mm?

This example I found on Facebook



I also pick up a mojo 20 sport turn fin. I will be making a new bracket.
How long do I make it? Stock bracket length or do I need to make little longer?

I noticed that the inside of the hull there is no backing plate for the fin. Do I need to add one? With the new fin do I need to use 4 screws or is 2 enough?