Just saw your post. I went downstairs and looked in my Benelli box for my shims. I have a "B" shim you can have. It's from my Montefeltro. If that one will fit let me know and I'll get it in the mail to you.
I'm not sure what the difference is but the Monte shims do not work or at least that what customer service told me. I am breaking it down tonight and will try my Monte shims...if they work, I'll give you a shout.
Don't you have an M1 and a Monte? Check out this web site. They show the same part number for the "B" shim for the M1 Super 90 Field and the Montefeltro.
I have 2 shims in my package that are labeled "B". A thin plastic one that looks like it fits between the stock and receiver, and also a heavy metal one of different shape. I know nothing about the shims as I've never had to use them. My Monte fits me perfect the way it came.
School was crazy today as we had a semi-epidemic of flu. We had over 22% absent, then I had Volleyball games to deal with this evening. I will break down the M1 tomorrow night and see if my Monte shims fit; if so, I'll give you a shout. Thanks for your help!
You are right, the C is the stock setup; however I was aiming low to hit targets going away...the B brought the Monte right were I needed it.