I have an upcoming flight on LX and called tonight in order to reserve seats. The agent asked me for my M&M number. I'm not a member of M&M but *G on UA. The agent told me that the even numbered A seats were blocked for SEN but told me - since I was *G - he could pre-reserve 10A for me. He said it would be about 90% certain that I would actually get the seat as requested.

Since you're *G as well you should just call LX and try to get your seat assignment changed to one of those single A seats. Good luck!