Tango you are definitely on the right track. That setup is right and should give you close to the 30moa you are after.
Just keep the ring halves together. Where people usually screw up is when they start mixing two different inserts on one ring (like -20bot and +10top on the front) trying to gain something. They are supposed to be used as matching numbered +- halves per ring like you suggested.
I've got a set under a 24Br Leupold on my mossy M44us. I ended up using the same setup you suggested to get approx 30moa except I used the
-10Bot and +10 Top in the front
+20Bot and -20 top in the rear
Either way will work but I ended up going with the smaller drop in the front because it gave me a wee bit more clearance I needed for the objective bell/sunshade.
It took me a little trial and error because the scope was so long and sits in medium rings. Once mounted it seems very secure and when I shot it I picked up somewhere around 25-28 moa of elevation over the medium Leupold rings I had on previously.
Gets me out to @225yards with subsonic 22lr match ammo
Ive still got approx 25 moa down left in the scope from my 25 yard zero so someday I'll pick up a set of high rings and go for closer to 40 moa using 20 inserts front and rear
They can be used to correct windage, elevation or both depending on the position you place the inserts, Gordo