@kaimotta : I understand you are styling mainly with css but have you tried setting sizes in the nature of
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text=""
android:textColor="# "
android:id="@+id/_name or something_">
</Button>
Something of that nature for setting the pre-defined attributes. Of course you would define your parent elements, and with a nav bar up top (assuming that it is static throughout the app?) base heights off of that.
I’ll admit i did skim through this and read a couple posts and the bottom, if im off the mark let me know.