That trail a bike on the Staton site was mine over 10 years ago and in fact while I was living in Crested Butte. Really wanted something that I could use when I wanted to and take it off when I didn't. It went ok in a straight line but when cornering it was less than desirable especially if you applied any power as it would want to highside the bike. I now run a BOB trailer with a Golden Motor 1000w 48v and it does nearly what I want it to. Using the axle as a contact point, both sides btw, is much better all around. Working with a friend on the next level of pusher trailer as after all these years messing around with small engines on bikes I still feel that the pusher trailer is a viable concept, for electric that is.
What I am going to do for long distance is to use a GX35, because 35cc is the limit in the state I live, in a friction drive setup. My first attempt at motorizing was a friction drive and it worked really well and I always seem to go back to what works I guess eventually
. If you are just looking for a kicker to get your load up the steeper roads you might want to consider a friction drive at least. It doesn't utilize your Nexus but with the right size roller it will definitely help alot especially if you pedal alongside it to keep it on the pipe. Don't need it, just raise it up and go with no parasitic drag. I have been noodling the idea for years now of a two roller setup but have not gotten around to actually doing it yet.
Two speed friction roller mount 1.jpg
Speaking of pipes the stock muffler on a GX35 is not too loud but you can use this technology to really quiet one down without losing power: http://www.piteraq.dk/flight/muffler.html
especially if you point it down at the ground at an angle.
But using a long bike with a motor on it is also a good plan and am excited to see what Dave comes up with down there for that.