What's worked for me is to create the LRF file in Calibre, and then use the Sony software to transfer the LRFs to my 505. I have an older version of the Sony software--one that still pre-processes the LRF file so my Reader doesn't have to do the work of calculating pages. Unfortunately, I think the newer versions of the Sony software don't pre-process the LRFs any more so this probably won't work if you have a newer version of the Sony software.
Oh, and of course, I don't have Calibre and the Sony software running at the same time.
dordale