A ridge line is the only way to go

Yes. A ridge line between two trees is the most reliable setup for a prolonged rainstorm.

Anything involving trekking poles or center poles will collapse under heavy wind or a puddle forming on the roof. A ridge line distributes weight and lets you pitch the tarp steep—which sheds water and wind way better than a flatter pitch.

The trick is tension. Use taut-line hitches on the corners so you can adjust without retying. Stake the corners low and close to the ground, but leave a few inches of gap for ventilation—otherwise condensation will soak you from below. If you’re on flat ground, dig a shallow trench around the tarp’s drip edge to redirect runoff.

For extra insurance, run a second line under the ridge line and hang a small drip line (a piece of paracord with a knot) so water doesn’t run down the ridgeline and drip onto your face.

Nothing worse than waking up in a puddle.