I wonder if you could get it close to "center" but putting the longer blade in the shorter hilt and vice-versa. Although, personal I think that would make it look wonky.
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I think uneven hilts works better than uneven blades. When you mix hilts it doesn't matter that much because you're basically making a single hilt out of them. mixed blades is more problematic, though I did see a guy wielding a "staff" that consisted of a normal 36" blade on the main emitter and a short 10" blade on the bottom. More of a sword with a short blade on the hilt, but still looked pretty cool.
But I agree, mixing a 32" with a 24" or such would probably look wonky. The example above wasn't really a staff, just a secondary blade on a saber.