How to set size of browser window in mwm?

Hi,
When I launch firefox in mwm on VectorLinux 5.8, its window borders stretch just a bit beyond the screen size. My resolution is 800x600. How do I fix this issue so that it always stays within the screen when I launch it?

Thank you.

firefox -height value -width value

edit: lol i just realized how old this thread was. :smiley: