Just wanted to give my $.02 that BookDesigner is a great tool. I use it for pretty much every ebook that I read, and reformat them into PDFs with the right page size for the iLiad and fonts that I want... etc. I prefer PDFs over Mobipocket for the iLiad because it's more difficult to pick the fonts you want with the iLiad's Mobipocket reader. I don't think BookDesigner will take an LRF as input though, so you'll need to grab a utility to convert that to something else first.
There's a section in the Wiki on conversion software. There should be several options in there that will work:
https://wiki.mobileread.com/wiki/E-book_conversion