In trying to determine the cause of the problem that Felix has reported when tiles use a lot of polygon styles, I have been looking at the code that divides areas into "subdivisions". The attached patch (applies to 1170) makes a few changes in that department. It is not expected to fix the polygon problem but it should be otherwise beneficial in that it will reduce the number of subdivisions created. Please do test this patch, especially if you are processing complex maps as I don't want to commit it until it's had a good bashing. I have processed all of GB and NL without problems.