overflow for peninsula

[dpg]

I'd like to do an overflow like this:

http://www.nano-reef.com/forums/lofi...p/t215859.html

except the top 2 returns would go through the overflow box and have antisyphon holes. Would there be an issue with the bottom 2 returns back siphoning? Anyway to tweak it? The tank will be 7x2x2 peninsula. 1.5" return split into 4 1" or 3/4" lines powered by a barracuda or hammerhead with 14ft head height.