[Phanx]

Actually, it occurred to me that you don't need to do any SetPoint work in the update routine -- you only need to set the point of each font string once, when it's created.

local lines = setmetatable({}, { __index = function(t, i)
    local line = UIParent:CreateFontString(nil, "OVERLAY", "GameFontNormal")
    if i > 1 then
        line:SetPoint("BOTTOM", lines[i-1], "TOP")
    else
        line:SetPoint("BOTTOM", UIParent, "CENTER")
    end
    -- do other stuff here, add shadow, outline, custom font, whatever
    t[i] = line
    return line
end })

All you need to do in the update routine is either SetText+Show, or Hide.