Mak 4 and 1 1/2" stand pipe question

[Delphinus]

Is your overflow 1.5" all the way to the sump?

I use a 1.5" durso/stockman overflow but under the tank the line is only 1" and it has two 90 degree bends. Let me assure you, that setup can NOT keep up with a mak4. I can overflow the tank with my mak4 on full (72g tank, 20g sump). The standpipe itself is not the bottleneck though, it's the plumbing underneath that's the issue. Just thought I'd mention that, because it's a significant factor. If I recall correctly I thought Dursos were supposed to be one size up from the plumbing so a 1.5" Durso is a good size for 1" pipe. Or something like that, I don't remember exactly anymore.