http://www.uoherald.com/news/news.php?newsid=207
Might also check out uoskins.com and the kr forums here. There were some good posts on how and why to install the Bitter Black skin. I recommend you download the Bitter Black 2.0 skin because the Bitter Black skin and Pinco's mods are bundled together and they are both quite good.
Once you have your userinterface folder set up for mods, the one you want to mod for fixing the corpse coffin and all other containers (except your backpack) is containerwindow.lua
I've changed the defaults to:
ContainerWindow.DEFAULT_START_POSITION = { x=1200,y=300 }
ContainerWindow.MAX_VALUES = { x=1280, y=700 }
ContainerWindow.POSITION_OFFSET = 10
but you can choose whatever x, y values work for your monitor size and location preference.
I also changed the following snippet to adjust how the windows offset by commenting out the x offset since I don't like the way the defaults tile things diagnolly:
-- else tile them like the old client
else
WindowClearAnchors(this)
WindowAddAnchor(this, "topleft","Root" , "topleft", ContainerWindow.CurPosition.x, ContainerWindow.CurPosition.y)
-- ContainerWindow.CurPosition.x = ContainerWindow.CurPosition.x + ContainerWindow.POSITION_OFFSET
ContainerWindow.CurPosition.y = ContainerWindow.CurPosition.y + ContainerWindow.POSITION_OFFSET