Worc,
Let's muddy the water a bit. The X2 I have with its sporting clays wood stock and 3.5" receiver has the "interface" to take the SC gun shims...got a positve answer from USRAC when I called gave them the SN and bought my shims.
I made the call after looking at all of the hunter X2's I could find and found that they all had neutral cast spacer between the stock and the back of the reciever.
It looks like somewhere between intro in 2004 and now the back of the receiver has changed.
Oh, well...glad to have mine it works well from clays to canadian geese. I hope these guys stablize thier product line as the churn must be getting some customers confused.