Maximumize seems to interprete the little titlebar controller windows as, well, as windows. :) This results in non-working Maximumize. Maximumize has an option to ignore sticky and already overlapping windows during the calculations. Unfortunately ignoring the titlebar windows of GMB seems not to work. Maybe there is a possibility to declare them as sticky?

Thanks,
Photon

I've made a small change (http://git.gmusicbrowser.org/commit/8180921a88) : I added the sticky mode, and set its type to "dock", each seem sufficient to make it work with Maximumize.
I'm not sure that "dock" is the proper type, it's the only one that had an effect among the types I tested. (see http://standards.freedesktop.org/wm-spec/wm-spec-latest.html#id2551529 for list of possible types).