Keenan, That is a beauty, and you did a wonderful job on a crazy piece. I'm gonna check my tree book and see if Syringa grows here. I enjoyed your build a long, and your pics. here are most informative.
You mentioned you can feel a little thump when shooting, and having made a few bows with the hard reflex in the grip I can relate to that statement. What has worked for me was using heavier arrows, and subtle tinkering with increasing brace height. I'm betting it shoots pretty fast, and the tiller looks perfect.
Rich