Flex / Leesbian,
1) I will get the cush hub info as soon as I can. I would not purchase the LC4 hub/sprocket carrier without trying them out. It is a lot of money to get wrong.
2) Your setup on your MXC looks great and is how my 525 will more or less be set up as well. Minimalist approach to bike packing. (I will never forget the comment in The Complete Backpacker, a weight conscious fanatic book author, that at one point he caught himself tearing the labels off of tea bags. My kind of guy!)
3) There have been many posts about the ability of the rear subframe to carry any additional weight. The Wolfman Minibag is one solution and the other is just don't worry about it. My RFS and my 250 2-stroke have been flipped over on their tails repeatedly, slammed to the ground, etc. without any damage to the subframe. I just cannot get worked up about this non-issue. (There were some recent posts of Europeans taking their MXCs with ProMoto racks to Africa with what looked like about 3 gallon plastic gas jugs attached. If you can fly over sand dunes with a load...really.)