I'm trying to increase the size of Window Button icons in xfce 4.8's panel.

I tried adding the following to ~/.gtkrc-2.0:

style "xfce-tasklist-style"
XfceTasklist::max-button-size = 70
class "XfceTasklist" style "xfce-tasklist-style"
This only seems to work when "Show Button Labels" setting is not selected. When the window buttons have text, the icons go back to being small. Is there a way increase the icon size when the window buttons have text labels?