I have used 4, 5, 6 and on one occasion an 8 string at a wedding. Fretted, fretless, solid body, electroacoustic & semi-acoustic. I've used a fretless Yamaha TRB6, A Modulus Flea bass, Rickenbacker 4000, whatever I happened to have at the time.
99% of the time no one will notice what you have as long as it fits in with the sound of the band.
I'd turn up to a corporate gig with a Warwick Bootsy Collins Space Bass if someone let me borrow theirs. Nothing is out of bounds as far as I'm concerned as long as it has 4 or more strings.