If you widen the teeth in the overflow, it should be able to handle more than 600. Alot of people run a 9.5 on them with no problems. I only run a mag7 on my megaflow with no issues. I just run PH
's in the tank too.
You don't have to have a big return but it can be nice
1. It was desigend that way and will be fine.
2. With the stock overflow, 1 950 will be all it can handle. Keep in mind, you will need to watch algae growth on the overflow. If you are running the drain at it peak, this can burn you if the drain slows down and the pump does not.
3. I have read some on RC about this but I don't think I would do it. JMO
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,