There are raised rollers that fit where the low rollers fit. The roller position you have right now is for the 25xx type tanks.
I had the same problem and used a rubber band and 3 120 film reels to hack together a support for the tail end of the tank untill I got the right stuff.
This is a picture of what you need. http://www.ebay.com/itm/Jobo-ext-arm...d#ht_500wt_922