I remember that one of the requirements is that the figure has to be weightmapped.

Load your figure, goto Figure (top menu) and click on "Merge All zones to Weight Maps", then save your figure back to Library. (Adjust the weightmaps if required) Then load your figure, and scale the groups/bones you want to scale up or down. Then drag-drop-conform your (also weightmapped clothing) with all options in its parameters palette checked ON.

That way the clothing will follow all scales as you wish. best regards, Tony