Pan F+ woud be good as it's inherently a pretty contrasty film, which will help prevent the positives from being too flat, although the best solution would be an Ortho film of some sort. Ilford Ortho+ would be great, or maybe Freestyle's new Ortho film... You could develop by inspection to get the right amounts of contrast you want.

Also the thickness of the sheet film over the thinner base of 120 negatives may be a blessing when handling the positives.