Plumbing/Overflow Advice

[SmallFry]

Hi, I'm asking for advice - again..

I'm repairing a 75 gallon aquarium as an upgrade from my 27gallon, I'm progressing slowly, but I'm in no real rush at the moment... So far I've discovered how to get the back panel out of an All-Glass aquarium - it's not easy, and that glass is stronger than I'd ever have imagined.

Now I need to work out what to do for plumbing as I'd like to get the holes drilled in my new back panel before I go too much further.

I've never had a sump before, so I'm not that sure of what is the best way of doing it. I've got some ideas though ,so I'm looking for input. So please tell me if my plans are good/dim but show promise/plain bone-headed!

I'm pretty much set on drilling because 1) I don't really trust a single syphon overflow box, so I'd need to run two, and 2) For the price of one syphon overflow I reckon I can do all my plumbing, probably buy the return pump too.

I've read good things about coast to coast overflows, so as I'm starting from scratch I thought I'd have one running the length of the tank. I'm thinking of a flow of around 800Gph - would two 1" drains be enough - or should I go with three? I'd like one drain to be able to handle the flow in case either should block.

I was going to create a durso type standpipe on the back of the tank with a T piece coming out of each bulkhead and the top capped with a small hole drilled so I can mix in air in a controlled fashion. From there I'd have a solid tube coming down to the back of the cabinet where I was going to run the final length with all the bends in it in flexible PVC so all the curves are smooth. The return would be flexible PVC so far, then solid, probably 1" pipe.

Most of the T pieces I've seen are slip together ones, so presumably that means I need slip bulkheads - how exactly do you fit your 1" pipe into these? Are they pushed in under friction, or are they glued? Would I be better off with a threaded bulkhead and a threaded to slip converter which could be glued? Sorry if these are dumb questions, but I'm a complete newbie when it comes to plumbing..

Fortunately I have more of a clue when it comes to building the stand/cabinet than the plumbing!

Thanks,
Rob