Just another thought after watching your video a second time:
Your bungie keeps the ridge line tight, but does not tension the tarp itself, who's initial tension is dictated by where you put your two prusiks. My understanding is that the looseness of a tarp is from stretch/relaxation of the silnylon, especially is cool or wet weather. It's probably much less from stretch/relaxation of your dyneema ridge line.
Your wife might like a set up similar to mine. The elephant trunks stay attached to the tree hugger. You just slip the end with the elephant trunk through the loop on the other end or the tree hugger. Hammock whoopies to elephant trunk. Tarp prusiks (or whoopies) to elephant trunk. Stake out tarp. Done! No knots to play with in the field at all.
BTW, I like the music on your vid. Relaxing...