The Tubus description of their rack says, "The ultimate choice for travelers when heel clearance is an issue. The lower mounting point improves the center of gravity and also optimizes the use of upper loading area. This design also facilitates mounting on smaller frames. Since bags are mounted further back, they permit more heel clearance. The variable attachment system makes an easy installation on nearly all frame geometry combinations."
Although not my first criteria, the advertised heel clearance was a selling point as I have had issues with heel clearance with many bicycle attachments for luggage. I am happy to report that the Tubus yields plenty of clearance as claimed. But, this is only the tip of the iceberg.
While shipped without instructions, (they are provided in PDF format on the Tubus website tubus.com) the mounting procedure is really very straight forward on a bicycle with eyelets such as my purpose built Proletariat which I had built specifically for commutation. Once I unpacked the rack and placed it on the table it was obvious how the thing hooked up. The process is quite simple, merely insert the screws into the eyelets loosely to allow final adjustment, connect the thing up how you like it and then go back snug everything up. Done. This process took perhaps 15 minutes.
This rack is very sturdy. I am certain that their maximum weight is conservative, but I doubt that anyone wants to carry more than 176 pounds on their bike anyway. Once bolted in place, this rack added a much stiffer feel to the back end of my bike.
Clearances are more than adequate and whether two panniers or one are attached, the weight is nicely distributed and feels centered in virtually all cases. Attachment points for the panniers are easily accessed and there are plenty of corners for attaching bungie customized loads to the top. The final nice touch on this rack is the large, flat, pre-drilled mounting plate for a rear light/reflector.
There are a large selection of mounting adaptations for bikes without braze ons available at extra cost from Tubus which include, clamp sets for seat stays, quick release mounts and other options.
I anticipate a great service life from this rack which thus far has completely satisfied my expectations.