I used some braided picture hanging wire in a modified Big Daddy I built. I wrapped it around the top of the motor mount and then up through the top centering ring. I added some scrap balsa reinforcement where the wire passes through the centering ring. I then put a loop in the wire to secure the shock cord. Here's a picture of the end result:
It's a very sobering feeling to be up in space and realize that one's safety factor was determined by the lowest bidder on a government contract.
— Alan Shepherd
I may be drunk, Miss, but in the morning I will be sober and you will still be ugly.
-- Winston Churchill