Jason,
I think it all depends on what YOU as the artist perceive as attractive.
In the left pic that you posted, you used 35 degrees for a double knot. . Looks good to me (if alignment is improved)
In the right pic, you used 45 degrees and I don't like it as well as the left, but it is OK and looks attractive enough.
In Brian's first pic using 52 degrees for a multi-loop knot (I think it is 8) and it looks terrific and I think he won a prize for that pen.
I assume Brian's second pic (Sierra) is also 52 degrees and, again, it's terrific again, for, this time, a double knot.
It actually depends on more than the size of the pen, and more than the angle. . It also depends on the number of laminations and the thickness of the laminations, in addition to the number of knots.
I guess only multiple trials will get you to what YOU like. Keep at it ... you're doing great ?