The key reinforcement is that the L3 project needs to be signed off before construction begins.
“TRA members designing or preparing to fly a level 3 project must present details of their design to 2 TAP members of their choice. BEFORE commencing construction, 2 TAP members must have signed off on the member’s certification form.”
Instructions are on the Tripoli Rocketry Association website.
Also, the TRA BOD voted to ban 3D printed fin cans from being used on level 3 certification flights.
This should not be a surprise since commercially available fin cans are already banned from being used on level 3 certification flights.