Hi there hamh.
After playing around with some of the free conversion software, here is what I've done (and it works perfectly...looks great on the 505!)
1. Download JE-Comics v0.8.0 and run it. Leave all the default settings as they are.
2. Convert the images to pdf (generate button)
3. Download/install pdflrfwin.exe and run it.
4. Assuming you know how to use the software, the only changes you will need prior to converting the pdf to lrf is 1.) under options, change profile to 'portrait' and 2. uncheck 'split pages'
This should do the trick and meet all your manga needs
-David