FYI the Shunyata’s SR-Z1 outlet is basically a stock Hubbell HBL5362, (20 amp), duplex outlet. It has good contact holding pressure but it is no where near that of Furutech Receptacles outlets or the Audioquest NRG Edison Duplex Wall Outlet .
As for making a diy cable support device I made a duplex plate plug single cup support like the photo on the left in this Link. Sonore Power Cord Support .
Though I do not have any big heavy power cords I made the plug support just to see how hard it would be to make. Hard to believe they sell for $80.00. Once I decided how I would make it, based on looking at the photo in the above Link, from start to finish it took me about 30 minutes.
There are three components that are needed to build the plug support unit.
* A good strong white non breakable duplex plate (Like a Leviton or Pass & Seymour.)
* 1-1/2" PVC repair coupling. 1-1/2 in. PVC DWV Hub x Hub Repair Coupling Fitting
(One coupling will make two support cups. So you could build two outlet duplex plate units.)
* Glue to bond/fasten the cup to the plate.
I used a Miter Saw to make the three cuts needed to the PVC coupling. With The Miter Saw from layout to finish making the three cuts it took maybe 5 minutes. Some sanding with 120 grit sand paper on the two cup tails to round off the sharp cut edges maybe another 3 to 5 minutes. (Only sanded the tails on one cup).
I’ll try to download a a couple of photo of the unit I made later this evening.