Label issues

I am having some issues creating axis labels. When I set horizontalalignment='right' (which is the default), the y axis label is positioned correctly for the left axis. Using 'center', the text is positioned too close to the axis so that multiline text runs into the tick labels. For the right axis (created with pylab.twinx(), it's the other way around - 'right' is too close to the tick labels and 'center' works better.

Any hints what I can do to position the labels correctly?