Sadly, the current Ussop's best attacks are his lies and the impact dial. Sure, he can make some nice flames, but any decently fast opponent at the moment should be able to dodge Ussop's ranged attacks.
What's more, the impact dial is useful against direct impact, whereas Kuro is a blade fighter, making that probably useless. And then really the lies usually work best on the less analytical opponents and Kuro was probably the smartest opponent in the East Blue.
So really, it comes down to this: Are Ussop's ranged attacks accurate / fast enough to hit East Blue Kuro? I'm not sure.