What you experienced is a drop in the whole system, not necessarily due to stretch in the Dynaglide; which, as mentioned above, is minimal. When using a ridgeline supported hammock there is always
an amount of drop when you load it. I noticed this with my Hennessey when rigging it according to the instructions, which say to pull the ridgeline tight. Once I figured out what was going on I learned to rig it with a loose ridgeline, at (or closer to) the 30° angle we all talk about. Rigging it this way does not cause as much drop when loaded and eases the amount of force on the suspension lines as well.
It's not broken, it's just how the system works dynamically. In order to be as close as possible to the tarp when using the hammock this way (tight ridgeline) it is best to take the tarp suspension lines below the hammock suspension lines with the main part resting directly on, or even slightly pushing/pulling down on the hammock. It looks funny when unloaded but as soon as you load it the hammock drops a little and the tarp will be very close to the hammock, the way you want it.
There are several threads on here the mathmagicians have posted about the forces involved in different suspension angles and many include the drop you are referring to. The search function here is your best friend; because even though I "get" it I have no idea how to express it mathematically!