I havesimiliar style HDbags. They too have the 07-08 fatboy styling... BUT... mine are about 1200 cubic inches instead of the 860 cubic inch ones you are getting. You should look into the slightly bigger bags (HD part # 88306-07)
I also have the detachable backrest/luggage rack.
Here are some pics of the HD detachable kit made for both the bags and the backrest...
This first one shows the studs with two sets of black nylon bushings in each stud. The innermost bushing is for the detachable backrest. The outermost bushing is for the bags.
Here are a couple where you can see all three mounting studs... even the lower one...
Also... the rear directional relocation kit is shown in the above photos. As can be seen, Harley has improved the looks by making a nice tapered directional light mount instead of just a stud.
I love the detachable bags/kit. It's so easy for both the backrest and bags. I'm glad I got them.
Good luck with whatever route you choose to go.