Overflow box/ Return pump question


Reefing newb
I will be starting my 40g breeder and 20g refugium. I was woundering if I should go with the eshopps pf300 overflow box, which is 300 GPH and a Rio 1700 return pump, which is 642 GPH, but with a 4ft head would be about 341 GPH. Does this sound right?
That should work. Just put a gate valve on the return pump pipe. That way you can dial it down if needed.