I have a Nelson-Rigg tail bag that I use on my '02. I remove the passenger pad and connect the bungee hooks to one another in an 'X' pattern under under the seat and re-attach. Works good and the bag is locked to the bike (although all a thief would need is a relatively sharp knife and they'd have it off in a second).
I've been using a Chase Harper Aero pack for 11 years as you describe. The bag comes with four bungee hooks sticking out but I took the cables out of the bag and put the hooks under the bottom cover of the bag and hooked/zip tied them together. This leaves me two bungee loops on the bottom of the bag. Take off passenger seat slide over the bungee cables, reattach and everything is rock solid. As a bonus nothing touches the body work at all and you can hook a bungee net to the cables/bag if you stack anything on top of the bag.
I've used this on my Hawk GT and 98 zx9r with no problems. Don’t know about a 6 yet as mine only comes in Feb but suspect you wouldn't have a problem as the 2000-2002's and 9r back seats are very similar. Only negative I have is the fact I only came up with this after the hooks had scratched the crap out of my hawks tail section...
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