Yes, two 4.5LBS will cook faster than one 9.5LBS
You could also reduce cooking by increasing your cooking temp. If you bumped up your cooking temp to 250, you'd knock a couple hours off your 13 hour cook
There have also been a few recent threads about smoke for three hour followed by braise for five recently. I tried it this past weekend and it worked really well. I used hard cider in the braise, and it was delicious. Family loved it, as did neighbors.
In the braise is their any beer I should stay away from or any recommended? Should I use water in the braise or just add more beer?