John,
I'm one of the guy's who did it and I doubt your back is any worse than mine. Four rods two cages and 8 bolts. I'm actual one and 1/2 inches shorter than I started out.
My back never bothered me one bit in our 3,000 + trip, what did was right between my shoulders and I mean it hurt like a knife being stuck in my back.
I sppoke with a bunch of guys at the rally about this and several suggestions were offered. I would most definiently go to newspeedmaster.com and buy the two and 1/2 risers for your handle bars I went with one inch and I'm paying the price now, they will pull your bars back towards you and allow you a more upright stance and it will take the pressure off your forearms. $70.00
Two, buy some type of throttle rocker or cruise control, believe me the ability to flex your fingers once in awhile and not hold on for dear life to maintain throttle during a long ride will be well worth the investment $5.00-$60.00.
You are never going to ever get away from "Monkey Butt" just the nature of the beast, but you can reduce it. Allot of guys go with a sheepskin cover, some go with a gel pad and one of our members has the air cushion, many just go with a new seat from Corbin, but remember weather it's the stock seat or a new Corbin it is has to be broken in and that takes thousdands of miles and many hours in the saddle.
$0 to $1,500
I personal use "Aspercream" before a long ride and find it really helps dull the "Monkey Butt" and those Icey Hot patches do not do jack but they feel nice, I went through two boxes of them.
It sounds like your trip will allow you time to reaaly enjoy the trip as so as you feel your moving around in the seat alott pull over and let some blood into that butt.
I hope this helps welcome to the site and have a great trip.
P.S. the pain did not start until we were well into the ride 1,000 miles or so and just got worse every day. Plus we did not ride in ideal riding condtions either if it was warmer and drier I would expect a different outcome, because you would not be screaming into your helmet "WHY I"M I DOING THIS, THIS S**K* !!!!

John