I've got one and what I did was to pack the scope mounts to obtain a raised back end.
What I did was get some " quick steel " from my local car accessories. It's a soft putty like a stick of black pool rock, you cut of a bit mix it together and in about 5 min it sets .
To use this you should set up the scope on your gun so you can zero the scope.
Wrap some cling film around your scope where it fits in the rear mount. set you scope turret where you want your zero to be, then put some mixed putter in the bottom of the rear scope mount and fit the top of your scope mounts nipping up the front mount but leave the rear mount loose .
Then comes the tricky bit .....start to shoot your groups they should be high if you have enough putty under the back.
Then by tightening the rear scope mount the putty will squeeze out end your group should come down.
When you get the group to where you want it leave the putty to set solid. Once set remove the scope and trim off the surplus putty replace the scope (without the cling film ) and your in business.
The down side of this way is you have to work quick.
On the plus side you will finish up with a set of mount with a pre-set down wards position and your scope clamp is still round and clamps your scope without distorting the tube.
If you do get it wrong you can remove the set putty and try again.