Decided I would like to get the tall HD17 inch sissy bar for my Superglide. Also the HD luggage rack. Wondering what kind of bags work well on a tall sissy bar? I see some square shaped bags but wonder how they work given that the bar slants back at a 15 degree angle. I mean, do the bags ride reasonably level, or do they tend to tip up in the back. Round bags work better? Anybody had some touring experience with some practical ideas?