Not 4 foot longer, but 4 foot lower. Lower in elevation than the intake. There has to be more water being pulled down by gravity on the back side than that being pulled up on the pond side. Not sure, but I don't think a long stretch going through the dam will matter as long as it is level or sloping towards the outlet some.
How'd you determine your flow rate for the siphon? Just curious, I couldn't figure out how to calculate it when I did mine. Couldn't find any online calculators for siphon flow. I found formulas, but they were all pretty complex.
