Wish I could help, but my 94 Road king is set up solo with a Corbin seat. I have fabricated a backrest the uses the mounting hole. I have also fab'ed a rack that attaches to the backrest support rod. Works great.
I have a T-Bag pack, with a top roll bag, that slips over the backrest and sits on the rack. I've used it on runs from Central Florida to Laconia with 40+ LBS of stuff in it.