Bruno,for an external overflow I think a stockman is best.
It's all about room.If you think a durso ill fit you can try it.
I have a few pictures if you want them.
Here's a few pics I took of one I built for my Eshoppes overflow.Just keep in mind the the shroud in the middle can be reversed so the open end faces up.I heard that even works better.
It's basically a reducer from like 1 1/4 to 1" pipe.I never glued any of it.
You have to kind of mess around with fittings at the H.D.
I was on a first name basis with the dude that worked there after a while.lol
I actually still have that stockman,too bad you live so far away.