Adjusting my scope

[backcountryj.laf]

I have a .243 that i've been shooting out to 600 yrds with a bushnell elite 4200 tactical scope on it, and i have a question that i need a hand fixing.

when my scope is sighted in i have about 14 moa adjustment up and 20+ moa adjustment down. I need the extra adjustment up to go beyond 600 yards, and i'm wondering what i can do to use some of the downward adjustment that i'm not using and move it up.

 

[KRP]

You need a sloped base or some Burris Signature rings.

 

[Eaglet]

The picatinny base looks like this:

Probably a 10 moa would be the one to use.
OR
With the burris signature rings you could probably use 15 moa which would give you a total upwards adjustment of about 29 moa and leaving about 5 moa from bottoming out when zeroed at (100 yards)?