Could it not be made 1.5in. pipe? Although with only 600gph, I suppose I could reduce it to the 1.25in.

1.5" won't give enough clearance between the pipe and the coupling for flow, you're better off with the 1.25", you should still be able top to push around 1000 gph through it.

I had the same problem with fitting the whole thing in at once (1.5 inch) due to the eurobracing. What i had to do was assemble it in the overflow chamber. Abit tricky to work with but was able to get er done..

With what type?

I had built a modified Duraso. I had cut the "T" and 90 elbow down to a minimum. It was designed to fit in the overflow chamber, which it would if I could get the darn thing past the eurobrace. :lol:

So its some type of straight pipe stack now.

I think I will go with the HGB, in the sizes Steve suggested.