This is similar to what we did at the Camporee, except I had to drape it over the tent stake the tarp out because we didn't have the extra two trees. It still worked well we were dry. We had a nice vestibule at the door.
Shaped tarps get boring after a time. Most are pre-cut with a specific shape in mind and they can only be pitched that way. If you are bored of the A-frame and pyramid pitches, then gather round and let me tell you about flat tarps.