you need the support brackets, get them on ebay
eBay Motors: Suzuki C50 M50 Boulevard Volusia SADDLEBAG SUPPORTS (item 120050851369 end time Nov-15-06 07:48:23 PST)
Or you can get either the easy brackets, or the ghost brackets. These are like 150 or so. but then you dont need the saddlebag supports and if you use easy brackets or ghost brackets you dont need the throwover for the saddlebags. you hard mount them to the bike. I would reccommend doing this it looks really good. a lot better than throwover. I made some brackets to hardmount my bags and really like it a lot.
easy brackets
Motorcycle Saddlebags / Saddle bag bolt-on hardware supports easy on/off system
ghost brackets
Ghost Brackets - Quick Release Saddle Bag Systems - Home