It varies from bow to bow, however, on a typical TD recurve like my Silvertip and Bighorn TD's the shelf is approx. 1" above the throat of the handle. On my GN Ghost recurve and my longbows with a bulged or straight grip, my hand placement puts the shelf right at my bow hand; right where I want it. The closer your hand is to the arrow the more it lends itself to "instinctive shooting". The arrow is where your hand is. G Fred talks about this in his first book. It is personal preference though, you can still shoot instinctively with an elevated rest, but when you cant the bow, your arrow radiuses away from your line of sight. It's very marginal though and like anything, you'll compensate.
Good luck, Kris