When I looked at the bike specs, it does say 20.5 pounds without pedals.
If you can afford the trip, I think a factory trip might be in order. I would be very surprised if you could not visit the factory and meet with someone. You might not get Georgina Terry, but you should get the time and attention from someone competent.
As for the custom issue...
The Georgina Terry bike has a hand welded frame as opposed to a mass welded frame from Taiwan. I don't remember the component mix on the LHT and what is currently on the bike you were looking at. Plus I can't check them right now, so I am no help to you there. There are a lot of poorly conceived and poorly executed touring bikes out there. The LHT has a good reputation, but I have never ridden one. And as I said earlier, I have no idea how Georgina Terry does her bike for 20.5 pounds. I don't think that if you bought a Gunnar and build it up yourself, that you would end up with a budget Georgina Terry bike. You should probably look at Rivendell too (also Waterford frames). They are on the west coast if that is more convenient for a road trip.
I have a Waterford frame. I got it, because I had a poorly conceived and executed touring bike. My original touring bike wiggled with panniers, and was a disaster. It was a great dirt road ride though. I can get my Waterford frame to flex, but it immediately dampens out all vibration. I put good stuff on it, and it stickered out at $5200 (frame was $2300). The ride is fabulous.
Most bike dealers do not carry touring bikes, so there may not be an LHT in your size to test ride either.
I think Georgina Terry's set up is in New York, so if you can arrange the trip you should. I know of someone who spent an afternoon at Co-Motion in Oregon, and someone who spent an afternoon with Seven in Massachusetts. At one point, my buddies and I were going to make a road trip to Waterford in Wisconsin, but it never happened.
