[texhax] how to use \pagefillstretch and its relatives

[Stan]

I'm trying to set up some macros that will print a full version and an  
incomplete version of a document.  The incomplete version doesn't have all  
of the material in the full version, but it should insert the right amount  
of vertical skip so the incomplete version's stuff lines up with the  
corresponding stuff in the full version.

I set up the macros so the difference in \pagetotal, \pageshrink, and  
\pagestretch between each skipped block are written to a file that's  
imported into the incomplete version and used to determine how much skip  
to insert.  I'm not getting the information from the stretches that I want  
when there's infinite stretching in a block that should be skipped in the  
incomplete version.  (I tried including \pagefilstretch etc. separately,  
but that didn't help.)

This would work nicely if, for example, the value of \pagefillstretch were  
"1" after an occurrence of \vfill (to indicate that 1 unit of second-order  
infinite stretch has been inserted), but since they're all dimensions, I  
need a way to write the dimension they take on after the page is ready to  
be shipped out.  Is there any way of doing that (or an easier way of  
achieving the same goal)?

Thanks,

Stan