@Bolingbroke and Martin Milner:there is at least one add-on for the new castles. It only adds one length of wall, BUT, if you look closely at the side opposite the double-doors: there is a second storey there, which means you CAN build upwards, doesn't it? 
Martin, I agree with you, this non-too square shape is a great step towards reality.
Cheers.
Arnaud
Unfortunately not. The 3268 Knight's Empire Castle has a second storey in the Keep section (at the back), but as it's all one big moulding there's no way to expand upwards. The walls have the battlements moulded in, unlike Steck walls where the battlements are a separate moulding. Thus the walls too cannot be expanded upwards. Only the towers are expandable vertically. I would be very surprised if the new system castles are any different in this respect.
It's good to know the curtain walls are expandable horizontally via an add-on set, that
may allow a degree of customisation depending on the wall sections, angles, and method of connection, but not vertically.
As soon as anyone gets one of these castles I'll be very interested to see some closer pictures of the connections and sections.
I understand that for child-length arms and small hands, there is a limit on how big a castle can be and still be played with. Since I am blessed with a lot of storage space, I may be able to keep these latest castles intact when put away. If the clips are strong (as the Dragon Towers are) it may be very difficult to take them apart, and this may be an advantage for moving them about, but I wonder at the storage space available in German houses and German children's bedrooms for toys.
