Tensioning Dynex rig

[Brion Toss]

Hi,
First, are you sailing in typical max loading conditions? The leeward shrouds won't go slack, even with a relatively slack rig, if you aren't loading the rig up. The typical max will vary with your location, so you'd tune tighter, for higher average windspeeds, in San Francisco, versus San Diego, for instance.
Next, what is the strength of that 7mm relative to the vessel's righting moment? If it is on the large side, you won't need as much tension to keep the leeward shrouds from getting floppy.
Finally, yes, Dux is less elastic than wire, at least when it is sized correctly. but it still wants tuning.
Hoping that John Franta will chime in here, too.
Fair leads,
Brion Toss