To let Finder always open a folder with default window width and height
This is extreme, but works: (see also Remove .DS_Store files from Mac OS X)

sudo find ~ -name ".DS_Store" -depth -exec rm {} \;


Restart and observe that newly opened finder windows are of uniform size. This deletes all ".DS_Store"'s. It then seems that they store relevant data regarding window size.

I did this partly out of curiosity, or maybe I have compulsive personality. I don't recommend normal users to mess up with your computer like this, though.