Some may laugh at me but I used tie wraps. Good ones... I have carried real heavy items in there with no problem.. My crate actually cracked on the bottom but not one Tie Wrap..
The nice is if you need to remove it... Grab the dikes and cut the Tie Wraps and in less than 30 seconds it is off... Then in a couple of minutes and the Milk Crate is back on... OH mine is a Pepsi one, black. I actually have two... A shallow one and a deep one.
BTW, I actually had mine attached to the orig Tdub rack first... It hung over the back of it by about 6 inches...
Lookeeee here, click on the picture to get a close up.