I just block each end with weights and add tape over the tube for security. like others, I use a 1/4" aluminum collar at each end. I wish the common hobby suppliers, Great Planes, Dubro, etc., made LH threaded 4-40 solder couplers in addition to the regular RH ones so I can adjust the flap-elevator by turning the rod. I know there are some short rods like that but my LHS doesn't stock them.
Btw, Mike and others, do you guys tap your ball links, or just force thread them with the threaded end of the pushrod? I usually pre-tap them.
Rusty