Thank you miamipanther for this detail and the awesome photos! I feel much better about wiring my prodigy brake controller.

So just to clarify... in the rear trunk, on the ride side, all i need to do is remove the "fuse panel cover (2)" per the BMW instructions above? Are you sure this will give me enough room to access that 4 pin connector so that i can cut that connector off and hardwire my prodigy? Also, does this "fuse panel cover" just come off easy without removing any screws or rivets or anything like that? that would be great!

honestly, i am not going to route all the wires through the vehicle trim, etc... i plan to just leave the brake controller in the trunk with a bunch of extra wire (like you mentioned about 18 ft) coiled up in the back with the controller. and when i'm towing (not very often) - i'll just grab the brake controller and bring it to the front of the car and leave it "loose" just for temporary use, not worrying about the wires just running through the cabin.

so i'm hoping the access to the panel in the trunk is easy, so that i can gain access to that 4 pin and do the wiring simply.

thanks again!