Leo Gürtler schrieb:
how can I force lyx/latex to put text on pages on which (floating) figures are placed that are greater than half of the page size ?
It seems that at some size figures are "alone" on a page. How can I change that to use every part of a page ?
You can change the values for the values \xxxfraction. E.g. insert to your preamble the command
\renewcommand{\floatpagefraction}{0.7}
to increase the threshold since LaTeX puts a float alone on a page. (If the float has >= 70% of the page height, it will appear alone on the page.)
LaTeX's float placement is a bit difficult, but it is well explained in chapters 6.1/6.2 of the book "The LaTeX Companion second edition".
regards Uwe