Well thank you sstorkel for the link and to fietsbob for the advice. I looked at that link, many pictures of loaded bikes, and went through a number of other things in me head to help. In the end, I looked over at the beautiful Velo Orange Camper standing next to me (kickstand that is) and decided that I didn't have enough room between the back of the seat and top of the fender to go with the larger Camper (24 liters and almost even measurement on height and depth) or Super C (23 liters, but even taller than the camper 28cm vs. 24cm). It's a 57cm frame, but I have the seat only about 7 inches above the top tube. Most bikes I see have more seat tube sticking out. I'm old school and prefer larger frame with less seat extension. There might be about 12 inches from the back of the seat to the top of the fender. With the support of the Bagman Expedition QR I should be just at or above the rear fender with the bag.

Also, I am a minimalist and this Nelson will probably provide plenty of room. If it does not I will be even more of a minimalist