you can setup visibility states for set lengths or attach a stretch parameter with defines intervals you can stretch it and restraints. attributes is possible but there are a few tricks when using them. for instance when you use attributes with visibility states the same attribute in various states must have a unique name. i think it is best to recreate the attributes while in the editor. I think you can reuse geometry from old blocks but recreate the attributes. I beilive you also need to lock the position of the attributes for the block to work properly. once you start playing with it let me know and i will try to help as there are quite a few undocumented secrets. good luck