Sorry, I'm late to the thread but in case anyone else is interested, the other way it can be done is to use the quick release solo rack OR quick release two up mounting rack made for 200-2005 Softail (on a 1996 FLSTN)

PN 53066-00C (two up)
PN 53559-04A (solo)

Before I bought it, I brought my QR sissy bar into the dealer, lined up all the holes, measured multiple times and confirmed it would fit. Duh. It does. So I have both setups. One for my long rides when I want a backrest and one for mama's purse when she comes along. Yes it's overpriced, yes there's other ways to do it that aren't from the Bank of MoCo but in case anyone else wants to **** money away like I do, this is the other option.