Gravity Feed Plumbing Setup Quest

[Hungriee]

I currently have a 20G Long sump with 3 chambers Skimmer>Fuge>Return but will like to move the fuge to a remote fuge. If I make a 40B into a fuge/frag setup, is 4-5" height enough to include a bulkhead and plumb the 40B to feed into the sump assuming the 20G is on the floor and the 40B will be 1" off the floor which will allow the 40B to have 5" height higher than the 20G sump.