I wouldnt jump the GPM up a whole lot. It makes for a really jumpy and jerky backhoe. Even if you can run your rpm lower you could be below the power band and you will need more power to run a bigger pump.
So I hooked up the new PTO pump and I'm running the tractor in the 900-1000 RPM range. The improvement in the speed and power of the backhoe is striking. So far I have detected no overheating problems and the backhoe operation is fairly smooth. I never tested the PRV to see if it was set properly for fear of dead heading/blowing the pump but I can only assume it is ok. I'm pretty happy so far with my decision to not spend $600 for the Kubota pump and instead go with the Dynamic pump for half the price plus I learned a lot about hydraulics in the process.