I think it has more to do with experience and weight/spring ratio.
With my two days experience, I reach a mighty 1 meter high
From what I've seen, with practice, 6 ft should be possible if you are under the weight rating.
If you are within or over the weight rating, you may bottom out before you can get that high.
If you're much lighter than the spring rating, it will take more work to get going, but you should be able to get good height.
Veteran bockers would know better..
