There is a way around most side-loaded format issues, provided you are useing Calibre, that will allow you to change fonts, change margins, etc.
1) From the Preferences menu in Calibre
2) Select "common options" from the "Conversion" menu
3) Click on the "Filter Style Information" tab at the bottom of the next page.
4) Select "Fonts and Margins" where it says "Select style infomation you want completely removed.
If you change "Miniumum line height" to 0.0% and "Line height" to 0.0 pt - you should be able to change line spacing as well.
If you try this, I would suggest you convert one of two books, load and test them in your device. If you don't get the results you want, you can always go back and change the fields to their previous values or select the "restore to default" button.
Last edited by fbrII; 10-08-2012 at 01:28 PM.