Liam
Your GPS receiver and ARTS transmitter will not function properly inside this rocket because the CF will act as an RF shield because it is conductive. The GPS signal will not get into and the the transmitter signal will not get out of the avionics bay without external antennas.
I also have to ask why you want to use an aluminum sled. It's conductive, heavy, and overkill. A good aircraft grade Baltic birch plywood sled is plenty strong, and if for some reason you want to go with a composite, use G10 FG.
I've been reading your posts on this rocket since they started. You need to be certified by either NAR or TRA to launch this rocket with L1 or L2 high power motors so you will need to find a local club and mentor to help you get high power certified before you can really use this rocket so I would suggest that you do it now rather than later. You need to obtain a FAA Waiver if the motor contains more than 125 grams of propellant and/or the rocket weights more than 1500 grams loaded. Doing this on your own will require 60 day and some paperwork. Once you are certified, you can fly with the club under their waiver and you don't have to deal with the FAA.
You can find a local NAR club here
https://www.nar.org/NARseclist.php
and a TRA club here
https://www.tripoli.org/prefecture/us.shtml
Bob