Injecting page-height to the FopFactory without creating a new instance

Hi,

We are migrating our service from apacheFOP-0.95 to apacheFOP-2.1. Our aim
is to configure pageHeight and pageLength to singleton instance during each
rendering call.

In earlier version we could create FopFactory instance by calling
FopFactory.newInstance() and then use setPageHeight/setPageWidth on the
same instance of FopFactory. Currently, this is no more valid. Now, we are
allowed to set these property on FopFactoryBuilder - new
FopFactoryBuilder().setPageHeight().build() which means we are creating a
new FopFactory instance each time. Is there any way of injecting these
property on already created instance.

PS: Also, i read a few issue where it has been said ApacheFOP is not
threadsafe and just wanted to know the reason behind it.

-- 
Regards
Arpit Phanda