I have been trying, without much luck to build a roll up style garage door using the LDD with the extended features. It refuses to let me put in the last slat of the door. If I put in all the slats, and then put on the horizontal slotted track brick, it won't allow that to snap into place. Strange. I am positive I am using the correct number of pieces, I've got the Fire Brigade door as a model.
If I leave off the top-most slat, then there is a gap, you can see through, after putting the parts to cover the top of the door. It's vexing!