Kindle Paperwhite: Collections and width

[fommil]

Hi all,

I've upgraded my Kindle 3 (the last one with the buttons on the side) to a Kindle Paperwhite and I've unfortunately lost some functionality from Calibre.

I was hoping that somebody could help me to address the following:

1. When I send all my files to the Kindle and then use the Collections plugin, following a restart, the collections are placed onto the kindle but they are all empty. The books are unclassified.

2. I'd like to change the HORIZONTAL_MARGIN to use up more of the screen, which I used to be able to achieve by manual editing of the relevant file in the system folder, or using the "Modify Kindle Settings" menu entry. Is there an updated way of doing this?