(RT) There are float placement parameters that LaTeX uses that are defined in thesis.cls. What they do are, to say the least, not obvious, as their definitions in the LaTeX manual seem fairly weakly correlated with the effects they have on figure placement. Anyway, these environment variables are in the thesis.cls after where it says FIGURES AND TABLES. For my dissertation, I changed \topfraction and \floatpagefraction in thesis.cls. Alternatively, you should be able to redefine them later with \renewcommand. I have
\def\topfraction{.9}
\def\floatpagefraction{.8}
The others I left the same as the original thesis.cls. This should embed more figures and tables in the text (i.e. permit the floats to take up more of the page.) Experiment with the variables to get what you want.