Hey everyone, glad I found this thread! Thanks for all the info, suggestions and pics.
I just picked up a model 1 for my 50g that I have not set up yet. When I set it up, I'm swapping out my uniquarium (Sea Clear System II) for a regular 50 that I'm currently modding to slot out the back at the top and I'm building an external overflow box that I'm going to attach from behind.
After looking at tons of sumps and DIY threads, I couldn't let go of the concept of the Proflex. Picked the Model 1 because it fits under my stand (dims are 36"X15"). It's small enough as it is, so I'm intending to run everything externally (return pump, HOB Remora skimmer, etc). Even so, the sump does not seems to have much capacity for backflow.
My biggest concern is the amount of overflow the Model 1 will be able to handle at shutoff. Based on my rough calculations (based on dimensions, since I have not put a drop of water in it yet), the third chamber can hold about 4.5 gallons. Subtract about 3" for necessary running volume, and that leaves about 3.5 gallons for backflow which is a nerve-racking narrow margin.
Have any of you figured out the actual backflow capacity for the model 1? TIA.