How I wish my choir had the range that your choir does, 'diverse379'!
My choir is far more limited in range, being a regular church choir. Here are the ranges that I am limited to with my singers:
Sopranos: "G" below middle "C" up to "E", top space of the treble cleff(an ocave and a fourth range)
Altos: "E" below middle "C" up to "C", an ocatave above middle "C" (an octave and a minor 6th range)
Tenors: (well actually, we're all baritones - if you're lucky, you'll get some REAL tenors, but we just have baritones who sing as high as possible) Top note: "F" above middle "C".
"Diverse379" was right about using chordal voicings such as:
"the triad built on the one
the triad built on the minor two
and the triad built on the four" - actually, using just the "I" and "ii" in different inversions, you can harmonize 'Amazing Grace' and LOTS of gospel songs - while the band plays other harmonies below. Yet another really cool thing about gospel music!