Under Siphon Specifics, I was asking if the siphon would work. It did. Now my question is, will it stop?

I drained the lake down, built sediment dams, etc. Lake is now almost full again. I'm not quite ready for it to be full again and would like to drain some water out.

I put the siphon through the dam with a 2" valve on top where I could fill it up and hopefully stop it by opening the valve. I ran 8" pipe to the deepest part of the pond and clear to the edge of a creek on my property. There is now a bigger drop and lot more pipe on the downhill side than previously. I'd like to drain some water out now; but someone raised the possibility that a two inch valve may not be sufficient to stop the siphon on a eight inch pipe with that much pressure. If I start the siphon and opening the valve isn't sufficient to stop the flow, it'll totally empty the lake and I won't be able to stop it. Any thoughts? Will a two inch valve stop an eight inch siphon with lots of drop?

[Linked Image from i108.photobucket.com]