I took some pics of these mounted in the rack before I start filling it up with other equipment. The rack is a Dell 4220 Standard which is 1070mm in length. That little thing on top of the two s6500s is a Dell 1U to give you an idea of scale, especially in the back. I'm using the 3rd Party Rail Kit for these minus the front brackets.
In the front shots you can see two QSFP cables plugged into the FlexLOM slot of the right node. Those cables should be the biggest thing coming out of the front that adds any length to the unit.
There are about 3 inches of space between the door and the front of the nodes. The blue Mellanox pull tab just touches the grill.
The dell is tiny in comparison. I'm probably going to end up putting these at the very top or bottom of the case so I don't have to jump over them with cables for other boxes.
There are about 2 inches between the back door and the fan tabs. I could've pushed these further back into the rack if I had needed the space up front but I'm not seeing the need.
Getting these in there wasn't anything special really. They're the size of a boogie board but they fit a normal rack just fine.