over the holiday break I reimplemented part of the xor float handling  so that
external float control is working again.

if somebody wants to try, the documentation in xo-pfloat is correct but in a
nutshell it works as follows:

 - specifying \savefloatplacement will write a file \jobname.fpl listing all
   float areas for each page and which floats went into them.

 - specify \readfloatplacment will attempt to read float placments from a file

so if you copy the .fpl to .fpc you can then change the placements by simply
moving the floats listed there from one area to another.

if the fpc file is not complete, eg has only specs for a number of pages, then
the algorithm reverts back to placing the remaining floats on its own.

saying it differently: if you start doing explicit placments this way you have
to do the placements starting with the fist page up to a certain page in the
document. right now you can't do placements only for a certain page somewhere
within the document and to be honest i'm not so sure that this would be really
such a good idea anyway since the chances are high that intermediate automatic
placements would invalidate the fixed ones very often

another restriction is that since the floats are inside the document the
placement spec will not work if you move the float to a position earlier than
it is actually seen in the document. in that case you would need to put the
float earlier in the document as well.

a good document to play around with the possibilities might be xo-sample.tex

there are certainly quite a number of ways in which such a scheme could be
extended and improved. the question is which are most valuable?

any suggestions and comments welcome.