Thanks for all the comments so far on my questions. I'm afraid I have to postpone some of the issues, however.
Now, I've got a different problem. I run accross a bug in layout concerning block-containers with height/BPD specified (absolute-position="auto"). I tried to fix it but I can't find the passage in the spec that tells me how to deal with the space that is not allocated by descendant FOs inside the block-container. Is this space considered as part of the padding-after, and if yes with what conditionality? The problem is page/column breaking. Normal blocks can be broken between lines which is probably also the case for plain block-containers (no properties specified). But as soon as the BPD is predefined (autoheight=false) it is unclear to me how to handle it. I also saw that in the 1.1 WD there is an issue (see block-container) that may be related to this, but it didn't help. Any pointers are appreciated. Jeremias Maerki