The current breaking specification doesn't appear to define a lot of detail for breaking of floats. I think a definition ought to answer at least the following questions (which are written assuming writing-mode: horizontal-tb):

• how do the rules for float placement interact with fragmentation, particularly when the widths of the fragments are different? For example:
  • if there are two floats at the bottom of a fragment that need to be continued in the next fragment, but they don't both fit in its width, which one goes first? (I would assume the earlier one in the document order.)
  • if a float doesn't fit within a fragment and it needs to begin in a later fragment, is it possible to place any other floats before it begins? (I would assume not.) In what order do such continued floats begin? (I'd again assume document order.)
• If a float's containing block does not exist in the fragment in which (part of) the float is, how are the edges of that containing block defined?