Still on the newbee side of the curve. But couldn't you modify the object file and reimport as a morph target. I realize that is using a different term..Add in the original question vs Modify. Regarding the original question, couldn't you copy and paste the bones for the original item into the added onto item (like you do with clothes) then add additional bones if required?

Gary

"Those who lose themselves in a passion lose less than those who lose their passion"