We're getting into practice now with my trio gone quintet. The doo wop group manages to avoid two harmonies hitting the same note because they have a bass, a baritone two second tenors (one of whom often sings in falsetto) and a first tenor. There's a lot of room between the bottom of the bass's range and the top of the falsetto.
My gospel group now has two basses, two baritones and a second tenor. There isn't enough room to find four harmonies without every doubling on a note, or hitting a note in the melody. Fortunately, the two new members from the doo wop group (a term I hate, too) are much more realistic, and relaxed about singing gospel.

The other complication is that we aren't always the same number of voices when we sing. We sang as a quartet last Sunday, sing as a trio tomorrow and all five of us will be working on harmonies on practice on Thursday. You really have to be quick on your feet to adjust the harmonies, depending on who is there each time. Sometimes we aren't.

Jerry

Thanks for all the observations. I am really enjoying them, and learning something along the line.