To ke the unit, you would take a piece of tube long enough for the the Nexus7 and the elbows to attach.
The insert the Nexus 7.
More often than not the it had to be propped up against something. Drcided to use tees instead of th elbows. Since both sides of the tubes were open, it led to a loss of volume, No problem. Found something to plu up the back sides of the tubes and viola it worked;