The patches you need are in the patch file called
libnickel.so.1.0.0.patch. It's just a text file and each patch has some helpful comments.
Reducing the footer is done by enabling the patch labelled
Code:
patch_name = `Custom reading footer style`
uncomment (remove hash # char) for the AuraHD/H2O lines and comment out the lines for the other Kobo devices.
If you would like the top (and bottom if required) page margins to stay balanced as you adjust the Kobo's left/right margin slider, you may like to enable the patch labelled
Code:
patch_name = `ePub adjustable top/bottom margin`
If, after reading the help notes you're still not sure what changes to make to the patch file just post your questions in
the fw 3.11 patch thread and I'm sure someone can give you detailed help. Alternatively, I use the above 2 options myself so if you need a ready-made
libnickel.so.1.0.0.patch file feel free to ask and I'll post it.