Scripting slices into prims

Is there any way of scripting a "slice" into a box prim using LSL?

llSetPrimitiveParams does not appear to support this particular parameter for PRIM_TYPE_BOX, and the "dimple trick" appears to be inappropriate when you want to slice evenly aboout a central plane.

Any information or suggestions would be much appreciated.

Thanks.

PS Er, how do I delete a post in the wrong forum, or move it to the correct one?