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Up to XOOPS 2.0.14, whether 'centre-centre' blocks appeared above or below centre R/L blocks depended entirely on the theme. It was one position, or the other. So if C-Left=1, C-Right=2 and C-Centre=3, the centre block will still appear above the others. To change this, you need to edit the layout of 'theme.html'.
In XOOPS 2.0.14+, you gained the option to put C-Centre blocks above or below centre R/L blocks when the block is created, but the theme has to be designed to support this new feature.
As xoops4u points out, the block weight is the weight relative to other blocks of the same type.
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