Bob, Ogre CS length is variable, in that it has a horizontal dropout with ~40mm of adjustment range for the case of an IGH with chain tensioning requirement. Surly geometry states CS=431mm, which is the most forward position, but you can effectively extend it to ~470mm (although with a derailleur it's going to work best in the 431-450 mm range, due to fixed location of RD hanger).

The actual rack mounting points are located a distance of ~440mm to ~460mm from BB center (there are 3).

http://surlybikes.com/uploads/bikes/fm_ogre_03.jpg

OP - If you want fenders, but haven't tried fitting them yet, you will find that the FD cable will interfere with fender if the wheel is mounted fully forward. You have to move it (and fender location) rearwards a bit to clear cable. Mounting the wheel and fender further back also makes it easier to remove the wheel with the tight fit you will have with fenders and a horizontal dropout. At this point you may also need Surly Monkey Nuts or a Tuggnut to keep the wheel from slipping forwards when pedalling.

http://surlybikes.com/info_hole/spew...nt_derailleurs

Back to topic, and on second thought, I think I would put a Tubus Locc on an Ogre, partly for the extra top length and width, partly for the neat way to secure a U-lock (assuming the right Abus lock can be found), and lastly it seems like the Locc would just look better scale-wise. More importantly, the Locc has more clearance height-wise and tire-diameter-wise than other Tubus racks and is better suited for 29er tires.

http://www.tubus.com/documents/13365...Classic_BM.pdf

http://www.tubus.com/documents/1323681562_Locc_BM.pdf