PFO pendants - height from water?

[Myka]

Hey guys, a year and half after setting up my 90 in Saskatoon I am finally getting around to building the canopy!

I have a couple of PFO mogul perpendicular "Optimal" pendants that I'm going to use. I bought them used awhile back so I don't have a user manual and I can't find one online. Does anyone know the manufacturer's recommendation for height off the water to mount these? The tank is 48" long and 18" wide.

They are this model: