What are the dimensions of the A320's wingtip fences? Does anyone know the size (relative to the wing) or have a schematic draw of these wingtip fences?
Dimensional information can be found on Airbus's Airport and Maintenance Planning Documents for the entire product range.

You will have to do a little digging and calculation to find the sizes of the wingtip devices but they are there.

Specifically, on the A320, subject 2-3-0 lists the height of both of the bottom and top of the wingtip fences relative to the ground, and 2-2-0 provides dimensions from the top.