Credits goes to Ugarik
The problem with the orginal calculation is that the height of Zoro and Buchi currently used in is wrong. We have reveived the official height for both these characters in the Databook (Oda-sensei) Buchi official height is 2.16m (7'1") and Zoro is 1.78m (5'10").
Pretty short and straight-forward
"I'm using this formula because radius and therefore area of the rubble was scaled from Buchi's height (^2 for the area) and the thickness from Zoro's height (volume = area times thickness)" - Ugarik
Previous result was 6.01477849904 tons
We can apply square-qube law:
6.01477849904*(2.16/1.8288)^2*(1.78/1.7526) = 8.52181122995 Tons (Large Building level+)
Conclusion: This scales to Buchi obviously (well, the Hypnotized key) and to those who scales to him or above him. (which is basically the majority of East Blue Saga characters)