Low math GRE subect test scores, but high scores on Major Field Test: Should I mention this in my letters of intent? I'm an senior math major in undergraduate planning on applying to around a dozen school's PhD programs in math. I think the rest of my application (grades, advanced classes, research experience, letters of recommendation, general GRE scores) is fine, but I am concerned somewhat with my subject test scores. Due to financial and time constraints, I was only able to take the test once, and I got a score in the 31st percentile. 

Is this something that's worth mentioning in my letters of intent? Specifically, I was thinking of mentioning that when I took the MFT (major field test) in mathematics as part of the capstone course at my university, I scored in the 96th percentile, so it's not that I'm bad at university mathematics, I just had test anxiety concerning the subject test.

Also, for what it's worth, I thought the MFT was similar in content to the math subject test, but not as difficult.

Another option might be just to mention the high MFT scores on my CV that I send in with my applications, leaving out any mention of that in my letters of intent, and just hoping that helps my case with the admissions committees.
Unfortunately, whether it's better to address it or ignore it largely depends on who is reading your application materials.  Some may want an explanation, others (on the more cynical side, and they do exist) may view any explanation as simply making excuses.

If you can get one of your reference writers to say something about it, it may carry more weight.  Of course this may not be possible depending on how well they really know you, but it's something to consider.

There's also the possibility that addressing it may not even matter since the school could have an unadvertised minimum GRE subject test score, where any application with less than that score gets tossed out.  Or such an application could go in the "maybe" pile, in which case an explanation could help.

My point with the waffling is it's impossible to say what would be better in general.  FWIW it sounds like you have a very strong application otherwise, so I probably wouldn't stress too much over it.

I strongly recommend this as your next step:  Seek advice from professors in your department who have served on admissions committees.