MLA research paper: letters or numerals?

In my paper, I'm trying to write 771,000. I'm told that in MLA, you should write numbers out if you can do it in two words, and otherwise you should use numerals. I'm also advised to use a combination of letters and numerals if the numbers are very large, however: 7 hundred and 71 thousand just doesn't feel right. That bit of the sentence goes, "particularly since the loss of 7 hundred and 71 over the winter of 2008-09". Can someone who knows these things tell me if I've done it right, and should stick to it, or if they would advise something else? It would be greatly appreciated!