Too much water in column will simply pull a vacuum bubble on the top and prevent a siphon. Think of a barometer, 30 inches for mercury sound familiar? It takes 34 feet of water to make a barometer, and you can test that with a capped pipe full of water stood on end, then accurately measure air pressure by measuing the water column height.

http://en.m.wikipedia.org/wiki/Atmospheric_pressure

Your biggest biggest problem I think is trying to get all that water moving before air creeps back up the outlet end. It takes a while to get that much water up to speed to prevent air from back feeding. Put a large bucket full of water at the outlet and submerge the pipe end, then open the valve. Air can no longer get up the pipe. Once the water is moving, the momentum can really push it over the hump.

Best bet is to prime the siphon from the higher water side to get it started.