http://www.startinglineproducts.com/instsheets/09-680.pdf
there is the link to the instructions for the pipes, but just so you know jetting and clutching on these engines with SLP pipes seem to vary alot from engine to engine. Even SLP says to use thier guide as a baseline to tune from. I run 380 380 370 but know of a guy that runs the same set up with 420 420 410. I know mine runs ritch, but I wanted to stay on the ritch side to be safe, I am ok with any power loss i have from it.( better then having to buy a new engine)
Ah yes, there is nothing like the sound of a piped Ultra screaming down the ditch, field, or up the mountain. Ultra's can be tricky to pipe and your 100 percent correct in saying that they are tough to get set up just right. One thing about the Ultra if your tune on your pipes isnt right on 90 percent of the time the sled is actually slower than it was stock in good tune with spot on clutching, gearing, and jetting. Your right in running somewhat rich though as the Ultra's really tending to lean out on Long pulls on the center cylinder. I think if I remember right we ran 3 different jets in ours with the middle being the richest for that reason.
It takes time to test stuff to see exactly what you can safely jet to by piston wash and plug readings, to me thats half the fun. Nothing better than getting a sled tuned just right then gain 5-7 MPH on top with a simple gearing or helix change. The ultra is a little heavy but it can be a sick sled when it works right.
While I will agree that each sled is somewhat different run ability wise the large jetting differences your seeing was more than likely due to the fact that he was running different needles than you. Jetting and clutching are things that have no set order of operation you can get the similar results with very different setups.
But with the same needles if he was at similar elevations he had to be STUPID rich provided you both run the stock air box.
Back in the day HOT TO GO did some big things with the Ultra I think they made both a 800 and a 900 Kit for them. those were SUPER potent. The 900 made 180 Plus HP in pump gas forum. That would definitely offset any extra front end weight.