10 lbs. should fit OK....if it scrunches up at the edges, just put a metal bowl or soup can with both ends cut out UNDER the middle.....hump it up like that until it cooks & shrinks up enough to lie flat.....
If you go to cut it apart, it cuts at an angle.....point is approx. the right one third in this pic....flat to the left side...this is lying fatcap down....
Here's where they've cooked awhile & the trim out is clearly visible......
That small area was all that was connecting the two pieces....
Cutting along the fat line will keep your grain for each piece intact....