Sorry i cannot try if thats correct my client was patched as above before 4.2 was even considered.
But personally i believe what will work with MPQ patches, is to just switch off zour internet connection before starting the patch
if it cannot connect to the server online it schould install zour patch files you have in the folder even if its mpq.
so disconnect zour router or switch of ur inet and just start the downloader or game i believe it will start to install the patch files u have.
Again i have no version to test it but u should try it