I wanted to know why it had to be inletted for a Winny, so I called the nice lady. She told me that some un-inletted stocks are "generic" in that they will accept any action inlet, and some are specific. The ones that are specific, have a different outside contour. Meaning that the ones designated for the Winny have a longer rear tang surface area than those designated for say the Remington.
The inner core/fiber sheets/gelcoat are the same on all the stocks.
That's news to me, as I have inletted many flat top McMillan stocks in the past, and have never had an issue. Perhaps, I had all the "generic" or the ones that were designated for the inlet that I put in...
Sounds like your stock should be inletted for the Winny or the Kimber in order to look/fit/function properly.