Sump/refugium dimensions advice

[Deep Blue Sea]

I am in the process of trying to build a sump for my 72 gallon bow front reef. The sump is 29 1/2 X 11 3/4 X 17 1/2 which are all the inside dimensions. I have the baffle glass all cut and those are 11 3/4 X 14 1/8, the extra 1/8 was a mistake on the first cut and was only supposed to be 14" but I allowed for the space between the head of the glass cutter and the actual cutting wheel in the wrong direction and ended up with the extra so I just followed this on the next cuts for continuity. I am planning a linear design and it will be intake, refugium, return. I have a return pump and it is a mag drive 9.5 and I plan to run some kind of an overflow box with the lifereef brand being my choice, but it is getting hard to come by due to shipping charges mostly. To drill is not an option just now since I cannot move it to drill, but on my first opportunity I will drill. The two main concerns and questions I have before I proceed any further are, is 3 3/8 inches of head space enough for overflow, and what size would you recommend for each chamber. I do have a skimmer, but it's a H.O.B. Aqua C Remora Pro that I have with no immediate plans of replacing because it's relatively new and not an expense I can justify right now and especially with the war department (A.K.A. wife) I am thinking that the most important chamber might be my refugium, am I correct? My thoughts were 8 inches for each the intake and return and the remainder of 10 3/4 after the bubble trap is added and you factor in the thickness of the four pieces of glass which is 3/16 thick. I don't know why I came up with these dimensions, other than they seemed to make sense with the little I did know about sump/refugium builds, which is extremely restricted. I welcome any advice or input and will be very grateful for the time you give me for this build.

[HaZRaTTy]

First off it was a hard read due to the lack of paragraphs but I got through it. (haha)

As for sump size my general rule of thumb is the biggest possible to fit in the space provided which increases your water volume and makes water chemistry easier to control and maintain.

Personally the chambers depend on a lot of things, I will never have a sump without a Fuge again. That is a personal preference. What are you going to be using in the sump? Reactors? Future internal skimmer? I would plan for that so you don't need to renovate and have the option to upgrade! Your refugium you don't want to have the entire return rate flowing through and should aim for 3-4x your system volume. (You could always bypass T connect your drain plumbing with a ball valve to controll flow through your sump.

The sump will be switched and controlled with an ATO? If not I would tell you to make your return chamber as big as possible or you might be filling it every other day which is a HUGE pain in the A$$.

If you're talking about the space clearance to the top of your sump to be 3.5 inches then that should be okay but I would make sure you plan for power failure and your sump can handle the backflow, also for extra security I would plumb in a one way check valve on your return so in event of a power failure you don't have a huge backflow it would be important to keep it clean and working these have a tendency to fail on some reports. (They're also really expensive)

Your first chamber coming from your tank depends if your using filter socks or just letting it flow into your sump on this chamber I usually only run a under baffle again a preference.

Baffles I would do some research into what you want I've came to the conclusion that an under over is all that needed and that 3rd baffle is just a choice. I have never had a problem with micro bubbles with just using the 2 baffle system

I guess to better help you, or make better suggestions I/we would need a little more information on what you're aiming at achieving in your sump. Also a picture says 1000 words and even a drawn picture on paint or a piece of paper does the trick.

Good Luck