Hmmmm . . . . works for me without an external RIP. In the configure printer settings window you get through the Printer Utility, I have queue set to ON, nest set to Optimized Order, start printing set to After Procesing. The printer waits a bit after sending a job to see if you will be sending more than one job that will fit the paper loaded. If it fits, the printer will nest them automatically. I make sure that each file has a page size big enough to provide the margin needed around each print so they don't get printed too closely together. There is not the layout control you have with a RIP. as the printer decides the exact nesting layout, but it is better than nothing. I sometimes will just gang images in Photoshop, though, too.
I hope this helps,
Ron H.