Hello.
I am not sure I am really qualified to advise, but I know when I am asking for help I appreciate as many replies as possible so heres my tuppence worth!
I have been accepted to do Soc. Anthropology at Cambridge - not sure how relevant my advice will be if you are not doing soc anth.
I put most effort and most word space into the rationale section. My dissertation from undergrad. covered a lot of the relevant readings, so even through I didn't end up mentioning that many in a name dropping sort of way, I think I could come from a fairly informed position (I hope!!)
My methodology was pretty vague, I simply mentioned the type of data I would be collecting and some ideas of the strategies I could use. Timescale was very vague - one sentence per year not per semester/term.
My problem, as always, is making things too long and complicated, and I really struggled to get it within a word count that I thought was acceptable. The overview, research questions and rationale were just too ambitious - my problem is I could see about a hundred ways to play with this project idea and couldnt bare to leave one out incase it was the one that would have turned the committee on. Eventually though, I got real and understood that it has to be clear and concise before anything else so I sacrificed a lot of stuff.
I got it down to about 3000 words for Cambridge application, and have since needed to shorten it for funding applications - currently struggling to get it down to under 1000 words.
My references cover about a page, single line spacings.
As I say, I can only talk from my own experience which is, ahem, limited but I hope this might help you think it through!
Rosie