Unwanted top/bottom cell padding before/after graphics in table

Toolset: fop 0.93, saxon 6.5.5, docbook-xsl-1.72.0

For a totally custom cover to our document, I've created a file book.titlepage.recto.xsl  which is referenced by the customised layer. The file specifies the cover as an FO table.  For example, the first two row each have two cells; the rightmost cells contain logos. Basic, but does the job for our purposes:

http://www.pasteserver.net/605

It works fine, except there is top and bottom padding in the cells, above and below the logos. As shown in the file, I've tried specifying zero values for "padding", "padding-top", "padding-before", "padding-bottom" and "padding-after" for each cell, with no luck.

I've added artificial background color to the cells, and turns both logos just to black, to illustrate where the unwanted padding is appearing better; you can see it as pink and green in this image:

http://img253.imageshack.us/img253/8499/coverminecd9.jpg

Does anyone know where the top/bottom padding settings might be inherited from and, even if inherited, why I can't explicitly set zero values to turn them off?

Thanks,

P.