It would run off of the overflow (no pump) and go through a beckett. Basically the same as a venturi design ....
http://www.diy-aquarium.com/do-it-yo...i_skimmer.html
that alot of other DIY skimmers are modeled after. Put a restricter on the out tube and "Y" it from the overflow, because I am not sure that it will be able to handle the entire overflow.
I am not too concerned about bubble cause it would still go into the sump and the baffles there would help alleviate them.
I would valve the "Y" to be able to shut it off for cleaning and valve the beckett also.
Return going about 4ft to the tank is a 9.5
Thoughts...width of main tube?