I have two questions
1. How did your passenger survive the trip on such 'comfortable' sit ? Not even sit, but was it acceptable without back support ?
2. Does your tank bag leave any marks from magnets on the tank ?
I had to build a backrest for my wife for the odd times that she rides with me. Every time I shifted, she said it felt like the bike was sliding out from under her. Also, I have to agree. My wife says that the rear pilon seat is the most uncomfortable seat she has ever sat on. Kudos to your wife for being able to do 600 miles. She must have buns of steel.
My wife is not your typical wife passenger. She has her bike, a 1985 Yamaha RZ350 Kenny Roberts replica. So she's used to riding sport bikes and knows how to ride front or back.
If not on the back of the Valkyrie, she would be on the back of this. This was a couple months ago at Deal's Gap.
She likes the comfort of the Valkyrie and had no problems with riding 600 miles while wearing the backpack. Although she said next time she'll not pack as much.
No marks from the tank bag. I think the key is to make sure it's clean before you put it on the tank and don't slide it around. lift it straight off and put it straight on. When the tank bag is not on the bike, don't lay it down somewhere that it can pick up dirt or other debris...of course nothing metal.