I really don't know what Harley was thinking with their 2 and 4 pt docking hardware. Painted it looks MUCH MUCH nicer for sure! If I was running a king pack all the time I would probably go with the Harley kit. For me, I use a chopped kit with a bag on top maybe 6 trips a year, so I went with the FBI kit. The FBI kit replaces the 2 and 4 pt kit, so you only use the FBI kit. For the passenger backrest you have to bolt an adapter plate onto the backrest, but it isn't noticeable. When you don't have the passenger backrest or tour pak on, you hardly can see the FBI kit.
The FBI kit used the shock tower for the front mount, and they provide a post that you screw into one of the factory 4 point holes for the rear location. I always questions if this was strong enough. I talked to FBI and they said they had only heard of a couple failures and it was from people that overloaded the mount. I looked at all kinds of ways to beef up the mount so I would be more comfortable. What I found turned out to be super easy, and made a major difference in strength.
When you order the Tour pak mount, and when you order the backrest adapter mount, each come with a set of post used to mount the units. You only need one set of posts as the TP and backrest both mount to the same locations. I took the spare set of posts and screwed them into the rear 4 pt mount holes. The FBI tour pak rack sits on top of these and adds a major amount of support. the posts are about 1-1/2", I trimmed the rear ones down to about an inch because that is all then needed to stick out. I only leave these in when I am on long trips because you can see them, but they are still way more consealed than the HD 4 post kit. Here is a picture of the rear of my bike with the FBI kit, I can post one with the extra set of posts after the weekend if anybody wants to see.