There are two schools of thought on mounting the relay panel. One school says that if you spend that much time installing it, and it's such an improvement over stock, you want to mount it where everyone can see it. The other school says hide it to keep the car as stock looking as you can.
For the later school, we recommend turning the panel upside down and mounting it in the same location as on the above mentioned web site, but hang it underneath the shelf. It's easy to get to there if you ever have to change a fuse or a relay, but it's out of site unless you are looking for it.
We've sold about 40 of these kits, and every one so far has been well pleased with them. I know of three cars with these kits that have been on the road for over four years with absolutely no problems.
However, if you wish to keep the car stock with a replacement harness, I highly recommend British Wiring (
https://www.britishwiring.com ). They sell a good product and they are great people to work with.
Dan Masters (Chief engineer for Advance Auto Wire)