One thing I'm going back and forth on is my camera. I have a nice DSLR that's not light (as DSLRs tend to be). But it feels like a missed opportunity to go on this trip and not take my best camera. I keep telling myself that I'm in super good shape, so I can handle the extra weight. But that weight does start to add up; a few ounces here, a pound there, and suddenly I'm carrying and extra 10 lbs!
Try to bring it if you can. When I did my x-country trip I was doing a lot of B&W photography. I carried a Mamiya 645 with a metered finder, power winder and 3 lenses and a 33mm with 1 lens, and, of course, film. I didn't regret it. Take it on your "shakedown" trips and see if it works for you.
BTW...Depending on the time of year, Trophy Bikes on 2nd Street in NoLibs may have several LHT's in stock. They may not have a disc version, but at least you might be able to try different sizes to get a feel for what might fit you best. And they have at least one employee that actually does some touring.
Let me know if you would like some ideas for weekend shakedown trips close to home, such as French Creek State Park. If you can arrange transportation, ACA's Atlantic Coast route between Port Jervis, NY and Philly makes a nice three day ride.