Full siphon would give you the pulling weight of the water volume of the tubing all the weight to the sump. That's way too much for any pump that you would use to pump water on the tank. Air has to introduce to slow it down. Well, in his case, using a valve to slow it down.
With my current setup, it is doing siphon 100% of the time. I have to use the air tube insert to introduce air into the pipe to slow it down. With the "slow down", it is drawing 3000 gph!
Unless you use a gate valve, it's gonna be very hard to dial it to "just right" to get the full siphon all the time, yet not to worry about the tank getting over flow... Oh, wait.. That's the Fail Safe is for. lol. ok.
Anyway, with durso standpipe, you can have siphon 100% of the time as well. Just need to make sure the are enough water volume between the tank and the sump and use an air tube insert to control the flow.