This motif is from the DMC Festive Tatting book.
As Frivole suggested, I added a half-ds to the small ring on top of the onion ring, so it would not be lopsided. Then I added two at the end which made it even better - good tip for anyone tatting this motif.
I tried a number of solutions, from SLT to an extra join here and there, in an attempt to accomplish a pleasing symmetry, but just could not come up with a workable, consistent solution.
In spite of the difficulties with this pattern, I do like the end result.
The thread I used is #40 Lizbeth. I have 2 almost-finished balls of #40, and it was a nice change from the finer threads I have been tatting with for months.