Each of the 4 points of the two rails of the snap-it adapter rotate in or out depending on how wide your racktime rack is. This is not done easily. It does not require tools, but it feels as though you are going to break it. I've never had to touch it since adjusting it from wide to narrow. See attached photo.
As far as the bag, I originally thought I could re-use the Topeak "dovetail" type slide in bag from a different bike/rack. I could have taken that dovetail piece off and screwed in the racktime rack, but the holes did not line up. I was afraid that I would have compromised the integrity of the bag. So I sold the bag and started fresh with a new Topeak bag with the velcro bottom. If I were to do it again, I would have cut a thin/sturdy piece of sheet plastic and lined the inside of the bag, then drove the screws through this part as well into the snap-it adapter.
Here's the link to ebay germany for the snap-it adapter. If you are using google Chrome, right click on the page and choose translate, unless you understand German. Not every seller ships to the US. You'll find one that will.
http://www.ebay.de/sch/i.html?_from...acktime+snap.TRS0&_nkw=racktime+snap&_sacat=0
I've seen other folks' posts on this topic. So far I've hear of...
1. Buy the city kit but replace the rear rack. $$ but you get what you want but have 1/2 the look of the city kit.
2. Buy the city kit and use panniers. Classy, just not my thing.
3. Buy the city kit but use a velcro bag. I did this for about a week. It got old real fast commuting every day.
4. Don't buy the city kit and use what you want.
5. Wear a backpack. Too sweaty for me.
6. My way - Buy the city kit. Pay 34 euros to ship a piece of plastic from Germany. Use the bag you want.
1000 miles so far and so good. Click/unclick and go is awesome. I haven't thought about any of the other options since.
Good luck.