Is this the droop stuff you guys told me about?

[5.5mm]

  Got the mounts for the 26-2 ,  weaver style rings came with the scope(a leapers utg 3-12X40 w/ao, locking target knobs, lit reticule, , etc,etc.. Mounted scope , good field of view, adjustments working. Came to zeroing and Scope won't give me enough elevation. It stays about 1 3/4" from poa, windage is working fine, got a nice little .5" group directly below the bull, but can't adjust elevation any higher.setting locks work fine, shoots that same group over and over, always an inch and 3/4'' low.
   Would a thin shim on the bottom of the front ring work, or do I need a droop adjuster mount. 

[ericw]

To correct for droop you would put a spacer under the rear of the scope, not the front.   The scope adjustments should first be put at the middle of the adjustment range.   When you run the adjustments out at the extreme of their range, your chances of having the scope hold "zero" are not so good.  You could experiment to see how much shim you need to get it close.  A quick way to figure it would be to add about .0045 inches of shim per inch of POI drop from POA at 20 yards.  This assumes your scope mounts are about 3.25 inches apart.  Some simple math here works wonders.
The risk with a spacer shim in the ring is that it will reduce the inside diameter of the mount unless the
shim is thicker on the bottom than up the sides in just the right shape.  Trying to mount the scope in the wrong diameter ring  could damage your scope tube.  It will work fine if you use some material that will form itself to the outer diameter of the scope.  Some try to use friction tape and another way is to wrap your scope tube with some plastic wrap and then set it in a thin bed of silicon sealer (aka RTV silicon caulk etc... the stuff that cures to a rubber) that you put on the bottom rear scope ring.  You would need to squeeze it down to approximately the right thickness so some good feel for what you need there would be required.  Let it harden and then remove the scope and plastic wrap , trim off the excess and mount the scope.   This provides the added benefit of providing a good "grip" on the scope. 
The other and simpler way is to just buy one of the scope mounts that is corrected for droop.  You take pot luck on the correction being just right for your gun but it can work out well. 

[Bullit]

Is it 1 3/4" at 5, 10, 20 or 30 yards?   That determines how much to shim.
You need to shim under the rear scope ring, and it will take at least 2 soda can thickness shims to make much difference.  You wanna get that scope back to center, because so much adjustment will kill it.  Here's a video from AIRGUN ACADEMY that'll help you out.  Enjoy and Good Luck to You !!!! Mike

https://www.pyramydair.com/air-gunsvideo

[digger]

If you are adjusted all the way up and still need almost 2 inches, you are going to need more than a shim.
Read what Mac1 has to say about it on his page. http://www.mac1airgun.com/droopers.html