Cantilever necessary for AR mounting?

I see that most of the popular AR Scope mounts are cantilever design.  Is this necessary?  If not, I would much rather use conventional picitinni rings.  I'll be mounting one of the low power variables with illuminated reticle.

Only problem with conventional rings is it is very possible you will not be able to get the scope far enough forward to get the proper eye relief.  Optimally you want the objective of the scope about even with the back of the upper receiver.

In this pic he put the mount on backwards and you can see how far back his scope is vs where it should be.

Obviously everyone is a little different and different scopes make work a little better with standard rings.  But in most cases you just cannot put the scope far enough forward with regular rings.




Here is one you can see with regular rings.  Look how far back the scope is.  WHile that may work somewhat when standing up, when you shoot uphill, sitting, prone, or bench you will not be able to get the right eye relief.



They make the cantilever style mounts for a good reason. 

Optimally if you are closer to this you will be better off.

If you'd like to keep low rings because your switching the scope between a boltgun to an AR, for example, you could get 1" riser mount. This will give you near perfect height and you don't have to buy high rings. 

This is what cheaptrick was talking about