I have just poured my ICF frost wall. I will soon be framing a doube stud wall on top. I had planned on putting a 2×12 sill plate on top of the 11-3/4″ thick ICF wall, with my 1/2″ wall sheathing flush with the outside of the ICF. This would have made the framing a total of 11-3/4″ to match the ICF wall below. It has been pointed out to me that the 2×12 sill plate will shrink considerably, likely warp quite a bit as well. This would pull my two seperate 2×4 stud walls together over time, causing them not to line up with the ICF below. a single sheet of 3/4″ plywood has been recommended, however, I don’t see that being very robust, and can’t imagine how I would nail my sole plates to such a thin layer? Anyone have any experience with this, or recommendations on suitable sill materials? See sketch below for clarification

Thanks in advance