Hi, just to stick my nose in, have you thought about making youre own? to fit where you want, that way you could use a larger bore pipe. I had a friend made me one for my sump maybe ste2k3 can tell me how to get a pic of it on here for you to see. Its running four wooden airstones from two dedicated twin outlet air pumps with a powerhead feeding it directly from the sump, its amazing and extremely efficient!
Mick