Changing OmniBrowser default Layout proportions.

I am using OmniBrowser in Squeak 3.10. When I click 'senders of' or 'implementors of' I get a window with the message list pane and the definition pane split 50:50 by default. How can I change that ratio to 30:70 and keep it as the default?

The full browser has four equal columns for categories, classes, protocols, methods by default. How can I change the columns to be of unequal widths by default.

Thanks,
Aik-Siong Koh