John,

I have also used the method WOJO describes.

Thought I would add to the thread that for a 2" focuser, built in vacuum systems use PVC pipe that has a 2" outside diameter. You may have to check a few pieces to find one that works as the dimensional quality control is not all that good. The good news is that most vacuum installation places / contractors have off cuts that they will normally give you once you educate them what you will use it for.

tjmck