A late answer is better than no answer at all, but sorry for the delay :(
I would suggest to look at the coming (soon) 2.30:
https://4js.com/techdocs/genero/gdc/devel/DocRoot/User/NewFeatures230.html#230Reportyou can configure this directly in your application.
Nevertheless, I would underline that printing via GDC is very limited and the report writer is there to produce much better reports than GDC would do.
Regards,
Pierre-Nicolas