My new favorite stumpwm best key binding:
C-t C-f : FullScreen
Also, I have remapped some keys to make them more emacs-y friendly:
(define-remapped-keys
'(("(Firefox|Chromium)"
("C-n" . "Down")
("C-p" . "Up")
("C-f" . "Right")
("C-b" . "Left")
("C-v" . "Next")
("M-v" . "Prior")
("M-w" . "C-c")
("C-w" . "C-x")
("C-y" . "C-v")
("M-<" . "Home")
("M->" . "End")
("C-M-b" . "M-Left")
("C-M-f" . "M-Right")
("M-f" . "C-Right")
("M-b" . "C-Left")
("C-k" . ("C-S-End" "C-x")))))