Need Input on HOB Sump Design

[DiverDude]

I've decided to add a HOB sump to my 29Gal bowfront. There are a number of reasons -extra water volume, a place for my new skimmer that won't take up tank space, a place for some form of mechanical filtration, a place for carbon and to put my heater.

I'm going to make it out of 6mm acrylic.

I have a few design issues I'm trying to sort out before I start building though and I'm hoping I can get some input from those here who have been there and done that !

Essentially, this will be a narrow, rectangular box that will be ~16" high x 18" long x 4.5" which will end up with an effective capacity of about 5 Gal. I'm planning on having several removable partitions for floss or sponge; to mount the skimmer on, and hold a carbon bag upright.

My questions centre around pumps and flow rates and managing the water level. The skimmer has a Maxijet 1200 (295 gph) so my thought is that whatever pump I use to pull from the tank, it should have a flow rate beyond that so I can throttle it (ball valve) to control the overall water height in the sump and to keep some flow in the sump so the skimmer doesn't end-up sucking up water it just skimmed.

For the intake, I want to do an overflow tube to skim the surface then come up, over the tank lip, through a ball valve, and empty into the sump (below the waterline to keep it quiet) into something like this sock holder. I'm thinking 1/2" pipe with a 1/2" to 3/4" adapter with 'teeth' cut into it for the top should be sufficient. Should I go 3/4" ? Ideally, I'd like to keep a powerhead out of the tank so can someone suggest a pump that I could mount on the side of the sump ? Would it be quieter/cheaper/easier to put a powerhead in the tank ?

Once water is in the sump, the skimmer is next: Bubble Magus BMQQ Skimmer. No big deal here; it'll just sit there and skim. Downstream of that will be a carbon bag and some sponge to trap any microbubbles.

My last question is how to get the water back to the tank. My initial thought had been to heat-bend the acrylic into a waterfall like on an Aquaclear filter or Remora skimmer. I'm second guessing that now and wondering if it would be better (more quiet) to do a bulkhead in the sump and have a pipe empty into the tank below the waterline. The hiccup with that is that I'll raise the waterline in the sump and it'd have to be an inch or 2 taller to accommodate. Thoughts ?

I think I should be fine for a power failure situation (water level in the tank and sump should be roughly equal at all times). Priming may be a bit of fun but I plan to put some kind of removable cap at the top of the intake to pour water down to get it going.

Anything else I'm missing ?