How many holes should I have drilled?

I have a 210 gallon tank (96'X24"X 21"tall). I had some problems with the center and one end cross brace coming loose. I decided the best thing to do would be to eurobrace the top of the tank. When I took the top trim off, I found that the glass was not even (had a bevel in it). A local glass shop says that they can fix it for me so I think that is the way I'm going to go.

Since I have to take the tank to their shop, I decided to have them drill it too. Right now it has a large hole drilled in the bottom to accommodate a single 2" bulkhead. I plan on covering it with a 3/8" glass patch. I'd rather have two 1 1/2" bulkheads with strainers for overflows and two 1" bulkheads for returns. I'm thinking of placement at about 2" below the top lip on the back of the tank.

I'm using a MAG 18 for my return pump. I'm also thinking of possibly adding a closed loop system for circulation. Would having additional holes drilled in the back weaken the glass too much? I'm using a Korallia pump #3 in my 110 and it works well. Would I be better off to just have the four holes drilled in the back and use a pair of Korallia pump#4s for circulation?

Your opinions and ideas would be appreciated. This is hopefully, the only time that the tank will be down for repair/modification.

 

Is this going to be a reef ? Just two vertical 1.1/2 pipes and strainers will not do a very good job of skimming the top surface of water for the skimmer to have at. I'd either do two corner box's or a single one across the entire length of the tank. That way all the water heading to the sump for the skimmer will be off the top inch of the tank. Thats where all the oils gather and the surface will be sparkling clear with no dead pockets with the oils and lint looking stuff that gathers in all tanks with the strainers just stuck up . And no way a mag 1800 or a 2400 for that matter will run this tank.. I'd get a real pump As for holes ???? About 8 if its going to be set up reef and then you can use a oceans motion for good alternating currents with in the tank. Check out Otty's 265 set up string..He has done all the work just follow his instructions or methods and no holes will weaken the glass once the bulkheads are installed its stronger. Like a Porthole does not weaken a ship. Or a drilled hole will not weaken a beam but a notch will