I need to add a little downward angle to get some extra MOA out of a two-piece base.

Do the Zee inserts work?  Do they put any undue stress on the scope, particularly with a two-piece base?

Thanks.

work great, I ordered the complete set, was shooting a 10/22 out to 350 yds and needed some major angles.
no stress on scope at all. you can go neg on one side and pos on the other for major inclines or just use front or
rear bushings to fit your needs.

they are a ball/socket self aligning, no stress on scope.  Work great on everything i've tried them on.

I've used them for years.They can be a little tedious to set up but once you get the right combination it will never change.
For maximum benefit you will want to start by " centering" the scope adjustments..........turn to STOP ,turn to STOP in opposite direction counting the CLICKS then set adjustment to midway.Do both elevation and windage turrets.Install the bases and bottom ring halves,using "0"(concentric) inserts ,set the scope in just the bottom ring half....make sure it is seated.Bore sight the rifle in a solid rest and see which direction you need to move the scope and mix/ match inserts to move accordingly.Remember,theinserts must be used as a set.......a +5 must be used with a -5.
It's possible,and I've done it many times,to have the first shot from a new scope mounting job to be within 6" of point of aim at 100 yards.
You might get lucky and get within 2",as I have done a couple times.
For what you are wanting to do they should work just fine.
I know I have a box full of '0' inserts and may have others.Let me know if you need any of those.
Good luck!

All I use on my match rifles and my hunting guns. Haven't used any other brand for several years. No damage ever to a scope tube or finish, solves alignment problems easy, no need for a canted base to get 20MOA dialed in the hardware. They're totally worth it.