I'm not familiar with SeedCommand or the 955, but i'm figuring the 955 is a cyclo too.  We used a GS2 and JD rate controller to do row-cutoff on a Case IH 950 last year.  We had a tru-count system on another planter, so i took the tru-count harness that ties into the JD rate controller (37-pin connector that branches out to four 6-way weatherpack connectors for controlling rows 1-4, 5-8, 9-12, 13-16) and ran voltage to a bank of electric air valves attached at the front of the seed hopper near the drum.  A bracket made by a fabrication shop in South Dakota mounts above the drum and holds eight individual air cylinders that each have a foam wheel that can be pushed down on the drum to push the seed out before it gets to the manifold.  Each wheel lines up with a row.  The electric air valve actuates the cylinder and pushes the wheel down on the drum, causing the seed to fall to the bottom of the drum.  We used a tru-count compressor and tank, but you just run the air to the electric valves, through the valve, and up to the air cylinders mounted on the bracket just above the drum.  You don't have to run the air to each individual row.

I don't have any pictures but could probably get some in a few days.  I read about this setup in a Farm Journal article. http://www.agweb.com/FarmJournal/Article.aspx?id=141219  ... some farmers by the name of Ellis in kentucky did it first with the help of Dr. Scott Shearer at the University of Kentucky.  I spoke with Scott several times while i was setting up our system and he was always very willing to help.  I have the information about the parts we used, contact info for the fabrication shop, in a folder at the shop if you would like that info.