I am thinking of scoping a Savage 220. Thinking of using a "Aimpoint" with a 2-3 magnifier. Any opinions on this setup. How about mounting problems? Thanks in advance.

The only issue I can think of off hand is finding a long enough rail to fit the RD and magnifier. At least, if the magnifier is an add on to the rear eye piece or is a separate attachment to the front or rear. There are rail sections one can customize but there aren't pre-made ones that I am aware of.

I've used standard scopes on my slug guns, I haven't had an issue with finding game in them and have been better able to use the range offered with a sabot. The scope has also been better with sight picture in low light conditions though I haven't used the highest end RDs in such conditions in a while.

Personally I would go with more magnification. That gun is easily capable of 200 yards.

I am not sure of your hunting location and potential shot distances, but I would look at it this way.... If you were using a 243 rifle to hunt that area, what scope would you put on it?

I started out with a 4X Leupold on mine.
It has a 3-9x40 Leupold on it now.
The 3-9 shrunk the group size considerably.

Similarly, my Browning A-bolt 12ga wears a 4-12 Leupold