Knightmoose......I couldn't help seeing your comments on relays. I would like to explain why auxillary relaying works and is safer and more reliable than "direct connection technology" since you are questioning it without comment. BTW, I designed relay circuits for nuclear power plants (including backup DC systems) as my first job out of college as an EE, and participated in redesigning a couple of popular manufacturers automotive kits as of late, so I know just enough to be dangerous to comment. I thought you would enjoy some info.
The idea of taking a 15+ amp circuit (for example) from the battery thru the fuse thru a switch/sensor then to the appropriate appliance has several inherent flaws or inefficiencies. First, most switches will not handle the amperage for automotive applications and especially in the space given. Yes, there are large bulky high-current switches, but they are very short lived and very unreliable compared to modern qualitative relays. Lower amperage switches are far more reliable and have multiple times the cycle life than much larger ones. It's hard to find a 10 amp switch these days that will take the continous and instantaneous loads and last any viable time. Secondly, rather than pipe the main feed, for example in a high current cooling fan, from the battery to the switch in the interior to the fan on the raditor is faily long routed by today's standards. Length is resistive and loses power over the length of the run. By simply running a signal circuit to a relay mounted on the fire wall (like the horn is set up)for operation, reduces the length of run, which reduces the size of wire needed and reducess the number of junctions and connections in the primary circuits, which reduces the voltage drops in the entire circuit meaning that the motor/fan/device will operate properly or at even higher efficiency with less battery capacity. Third, the availability of the main battery buss under the hood is most convenient with all the signal circuits coming from the interior or peripheral devices. Forth, because these long wires that are directly wired can carry in excess of 20 amps, there is need for cooling of the wires and run in their own bundles and that is hard to do under the dash. This is why ALL OEM car makers do NOT use an amp gauge any longer. This is much easier achieved under the hood and in case of a problem with that wire their is much less risk under the hood of a major burn down. Fifth, high quality, automotive relays are designed to take the cycles (most in the hundreds of thousands of cycles), operate in higher temperature environments, have innert or sealed contacts, have higher contact areas per amp, and have built-in timing mechanisms to help them quench high voltage spikes when circuits are switched open or closed whith can kill computers and other electronics. In terms of MTBF (Mean Time Between Failure)of a circuit, relayed circuits when designed correctly will have a three to five fold MTBF over direct switched circuits for all of the reasons mentioned above and a few more.
As a final testimony to relay technology, just open the hood of any OEM automobile and look at the relays they have incorporated there. It's state of the art, reliable, safe technology.
As another comment on high capacity fuses for inductive circuits (motors). For proper protection, most inductive high current circuits should be protected by themal breaker technology rather than fuses. This is because high inductive inrush currents, especially in motors, can blow fuses easily and usually to offset this normal condition most people "overfuse" the application. In other words, they just put a larger fuse in. Sometimes this works, but is not ideal and offers compromised circuit protection. Most,if not all automotive breakers will not trip on these short inrush currents and can be designed to more closely match the motor circuit and have the advantage of automatically resetting should a problem arise.
NOw, this may seem a bit too long...but I just wrote a big dissertation in Northern Rodder Magazine and Southern Rodder Magazine on this very subject. I hope you will reconsider your view.
ConceptOne Pulleys and Brackets
Northern/Southern Rodder Magazine's "Jack'Stands" author and creator
Techical forum/links at www.inccn.net/techforum.htm