That is the whole point. You can't do a long 9k pull. It isn't possible. If you look at the rating by layer, only the first layer is capable of 9k. It also has a minimum number of wraps (usually about 5) before it can be loaded to full rating. That leaves you with about 7 wraps or so around a 3" drum or roughly 6' where you can actually achieve a 9k pull. Think about that for a second. You have to find an anchor point that is exactly the right distance away so when all the slack is out of your cable and everything is tensioned so you can use your winch at it's rated capacity, it will only do so for about 6'. When the line jumps up to the next layer, the capacity drops roughly 20% because the effective diameter of the drum has increased and the leverage is now against the winch motor.
4/0 isn't the problem. The problem is again, knowledge does not equal understanding. The fact that you reference a long 9k pull means you don't understand how winches work but you have a good working knowledge of electrical theory which is nothing but good but you also need to temper that knowledge with the understanding of how things work and why you will never see a 400 amp draw out of your winch.
Yes, I design products, a lot of them and I've been at it for a long time. My goal in every design is to make something work very well without it being overkill that adds unnecessary expense/weight/ or some other attribute that renders the design inelegant. It is easy to throw weight, size, and bulk to a design to overkill it. Just look at some of the control arms out there. Skill and understanding are required when you want a design that is just big enough to get the job done and no bigger than it needs to be.
Looking at what Warn has done with the remote winch hook-up kits, it looks like they do similar. They have an understanding of what works and size the wire accordingly so it isn't me that knows best.
