Nice job, my piece of fresh preshaped (reflexed) ash is waiting for something similar.
You mention that it shoots better with the arrow nocked perpendiculary to the handle. That perhaps indicates that the lower limb is bending too much. This way of nocking is definitely not the correct way (Im being taught Kyudo).
I understand that you were curious about the design while sticking to your usual way of shooting, but I suggest you consider the japanese style while shooting a Yumi. Besides the not-crucially-important principles, there is actually one more reason for incorporating such an asymetrical bow design and thus, the angle of the wrist, being tilted cca 65 degs, as if punching the fist. The Yumi is pressed just in between the thumb and forefinger, not the bottom of the palm as you appear to do it.
Then, of course, much longer draw is used (arrow length measured from Adams apple to the fingertips plus 5cm), resting from the right side of the grip while drawing the string with thumb (in a glove) pressed against the middle finger and forefinger pressing the arrow in a rotative manner... but thats kind of ridiculous to explain, since its a manner of years to acquire the correct technique.
Good luck with further jobs!
