when your applying for ILR, you better take or send more than 6 letters or documents as evidence you've been living together for 2 years, i've read a few posts where people have gone to PEO's and the case worker was not happy with some of the documents that were produced, even thou some were listed on the app form as acceptable types of evidence.
reasons were the letter was not printed with any coloured ink on the pages, so it could be a copy, a bank statement was not strong enough evidence that you live togther.
so take or send more just in case their not happy with what you produce. i wondered if this would happen, as they reduce the numbers so much, would they be stricter on what evidence you produced, maybe its just teething problems
when i applied for the misses, i sent at least 30 bits, every bit of evidence i had with both our names on, most of the docs i had with the wife's name on and the rest with just mine name on, at least 1 for every month of the 2 years.
i don't know if they would refuse your app for this, but incomplete apps is one of the main reasons why apps are refused, as for some visa types ,they will not ask you for extra evidence, they will judge your app on only the evidence you just submitted
so be wise folks