I have someone willing to build me a custom 280 or 300 gallon tank to my specifications. I have run many 125g or bigger tanks before but all with canisters. For a tank this big, it just seems ridiculous to run 3 canisters (FX6's) since that's a lot of maintenance I'd rather not be bothered by. So for filtration, I am thinking of running a FX-6 that I will be taking off the 220g that I am selling along with a wet/dry filter. I have never designed or set up a wet/dry filter before so I need some help. Since I have the FX6, I'm thinking of using a 55g tank for the wet/dry filter. One of the LFS I talked to suggested I have dual overflow boxes inside the tank on the sides and run 2 PVC pipes to 2 different spots in the wet/dry filter. The question is what size bulkheads I should use and how much GPH I need for the return pump. How is the GPH determined and the water level set etc, please help this noob out
Here is what I have come up with so far:

Here is what I have come up with so far:
