Gerahead's 71 Dart

Question for you guys on headliner installation. I have the style that has the bows slipping into a set of three holes at different heights in each bow location. The headliner was removed prior to me getting the car, so I don't know what the previous locations were. I have a set of bows from a boneyard donor that I marked for position when I removed them. How do I . . .
- determine the correct hole to install the bows, height-wise?
- do the bows all need to be installed at the same height?
In dry run, the center bow hits up against the roof when I use a set of holes that both ends of the bow will hold up in. Are they supposed to ride up against the roof and "flatten out" by design? I've done a headliner before, but didn't have this issue because I took the old one out. Thanks for your help! L8r

Jim