There are all sorts of permutations of formatting for an NSF proposal. I've tried many, and my favorite was Arial, 10 pt font, and 1.5 line spacing. The proposal looked great - but my program manager said it was too sparse and needed more words.
So now, I'm working on my CAREER adding 'words' to fill in the gaps. And now I find myself at 10.5 Times font with single spacing. Is that too small? 10 is the minimum font size, and I think that 10 is really tiny for people with reading glasses, etc.
So what is your favorite formatting for an NSF proposal?