for what you want aai think I would replace the stock diamond with a rectangle with a ridge about the same length or just a bit longer. The idea is to leave it attached the way Hennessy does. Door flaps would be useful on the head end. Both ends if the weather changes that much. Make the sides long enough to go to ground from a comfortable ridge height. There are a couple of ways to deal with the suspension. I like the idea of looping a strap around the tree and using a carabiner or Dutch clip to close the loop then a buckle setup tied in after where the tarp ties in. That gives you a drip break and adjustment point. I'd go with Polyurethane coated polyester if I had a choice. It takes the sun better than nylon. Stuff the whole setup in a large Bishop Bag. In practice pull the bag out of the vehicle, snap one strap around a tree. Feed line out past the buckle where you can guesstimate adding slack. Keep feeding to the other buckle then tree. Close the loop. Walk back setting the sag at the buckles. Stake out the tarp corners and hammock guys. Step back, pull out chair, grab a cold beverage and sit and watch your neighbors working at setting up. Took longer to describe than it should take to do. No knots, minimum fiddle factor.
Want even less fiddle factor put rope pockets at the tie out points on the tarp. Use permanent ropes for porch mode left tied on with tautline hitch on the far end. Going to ground just stake through the tie out loop. Porch mode - stake out the rope end and adjust.