Tenors usually sing in 3rds above the melody line, an octave down, which works out to a 6th below the Soprano notes. If you can make chords with the melody note on top, Gospel voicing usually is -
Sop - top (Melody)
Alto - middle (Harmony)
Tenor - bottom (Harmony)
I think lots of guys have to switch to their Head/Falsetto voice to get up there, no shame in that, most will sound a little thin up there.
I tell the Choir to think of that old 'Hefty' garbage bag commercial, "Hefty, Hefty, Hefty" (chest voice), "Wimpy, Wimpy, Wimpy" (head voice) to illustrate it.
I agree w/Joan - in our small choir we have a couple of guys who sing bass/baritone, and I tell them to sing the melody...