I've read with interest the dialog with respect to bazooka tubs and copper manifolds. With respect to square or rectangular coolers I think the easiest and cheepiest way to go is with 1 inch PVC Pipe and fittings. PVC is easy to saw with a hacksaw. and I drilled a zillion 1/32 inch holes. The pipe slides easily into the fittings and I used no glue so that the manifold can be easily taken apart for cleaning. Just like children's tinker toys. No soldering or welding and PVC is as cheap as dirt.