If they removed the outer wing sections of the C-47 the Chinook would have probably lifted it , the down wash onto the flat wing area increases the load on the hook of the lifting a/c , the crew of the Chinook should have known that , there is a formula to work out downwash weight increase on flat areas most airmovement training units in the military should teach that!
The Australian Airforce learned this years ago lifting crashed Caribou and A-20 Bostons in PNG
The Columbia Chinooks have there external tanks removed for just this reason, reduce downwash force area to increase available lift, the oposite of this is the large tanks on the MH-47 and Singapore CH-47 give great range but reduce available sling load.