I was informed that in order to shoot a Canon 5D with 17-40mm lens set at 17mm that I would need the 20mm t-adaptor as only using this adaptor would I be able to set the camera at 111mm on the upper rail (this is the suggested setting as per http://www.nodalninja.com/html/canon_settings.html). I wasn't told, however, how to mount the 20mm t-adaptor, so I guessed:

Question #1: Did I mount the 20mm t-adaptor to my camera correctly?

This brings me to question #2: Which hole do I use on the 20mm t-adaptor to mount it to the upper rail (refer again to the photo above)? I guessed the hole closer to the camera--the one with the center-line mark. If I did actually mounted the plate correctly, please confirm that it is now properly aligned at 111mm as it's supposed to be:

Lastly, the upper rail, when the gear is mounted, slips slowly even after I tighten as best I can. Solution?:

Thank you for your help--I need it.