I've been using one for years. It's a fantastic piece of glass. Peter Ward started using one on his old RC and I bought one. Never regretted it. Got rid of all my barlows.
The only thing you need to do is place it at the native focus plane of your scope then add tube extensions for magnification. There is a chart for this on the astro physics website. Practicaly I never went past 4x for DSO but for planetary you could go up to 8x. I use standard GSO extension tubes. 50/80/150mm.
I barlowed my
GSO 8" newt and the
FSQ as well.
It holds magnification spectacularly well with no light scattering whatsoever. Even in
IR.