Wonderful post, Ymryl. Beautiful rig. Very useful info. I'm towing a 24 ft. equipment trailer loaded with a Kubota 50hp diesel tractor and whatever impliment happens to be attached at the time. The 8 ft. multigang disc is the heaviest. Tractor tires are filled with water for traction and stability, so it's pretty heavy. Total weight is about 8,000 lbs.
I only tow short distances, so I have not been using an equalzing hitch. The Prodigy brake controller is the way to go and I love mine. While I'm not having any stability problem with the short tows, you have me thinking about the Equal-i-zer. I was just about to buy a Draw-Tite, but will rethink that.
Here is an interesting article I found about how well our Armadas do in towing boats weighing close to 8,000 lbs.:
http://www.trailerboats.com/site_page_1483/article_page_278.cfm
It pretty much confirms our experiences. The independent rear suspension is great and those airbags on the shocks do a great job of leveling things out, but I don't have a lot of suspension travel left with the trailer attached. I have not measured tongue weight, but probably should do so.