Andy,
If you had not sold your Morrison I could tell you no problem! But them there Shrews are just fine as well in cold.
Coldest we had so far this year was -18, but have hunted -25 with never an issue. I do leave my bow in garage, unheated rather than in and out of heat every day at this time of year. New foam/carbon limbs fine this year as well.
Biggest issue you will have is drawing bow back. Probably not something you have experienced, does not effect everyone. But many people, after sitting in cold for two three hours then grab bow at critical time and can't draw it back. If you can get away with movement best option is to draw bow back every half hour or so while on stand. Another option is these lovely heated pads that stick on (for muscle sorness - in drug store) when it's real cold stick one on shoulder area keep blood/muscles warmed up.