Ok, here's the news.. the good, the bad, and ther ugly....

Good: makeshift bulkheads seem to work great, with no leaks! Yay!

Bad: Sterilie got a crack from the water weight in the lip on the top..
once the lid is secured on, I think it'll reinforce it fine.

Ugly: the water flow in exceeds the waterflow out, so I'm getting
overflow.. only options I can think of is trying a larger output fitting,
adding a second fitting the size I currently have. I'm using the largest
hose my Lowe's carries, so I'll need to also rig up a outflow pipe or hose
to the pond.

I could use the toilet flanges I got, but I'm still not happy with the wax
seals on them. I'm going to see if there are some 2: fittings that might
work out in the electrical conduit section, or the plumbing section at
Lowe's. I'll need to see if I can use something that will still accept
that makeshift gasket from the web page article.

Hi Garee - IME, a 2" return fitting will handle up to a ~ 2000 gph pump - if
you are pumping more than that through the filter, you need more than 1 - 2"
return line, but more than ~1000 gph going through your filter of 45 gal
will be a problem as it will not work as well (too fast) - I use a 2500gph
pump that is "teed" so that I am actually running ~ 800 - 900gph through my
45 gal barrel filter and the rest directly to my waterfall
Gale :~)