I like 5 best, though if you have a HUGE band I can see why you'd have up to 8. My line has 4 basses due to not having enough people, but it's working just fine.
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Vista Ridge High School, TX
Freshman 08-09, Quint section leader (though I am the only quint player

)...3rd at PASIC High School Standstill with best snares.
Our line's [small] numbers;
basses:4 snares:4 quints:1