At CARTERANDSONSLLC.COM we suggest one of two different solutions...
A. We offer a spreader bar; that is basically a large turnbuckle. It connects to each EZ-HITCH and adjusts the arms to the proper distance needed for each implement, and then keeps the arms at that distance. Using the spreader bar will also allow the user to bump the implements into place if you fail to line the tractor up perfectly with it.
B. You can simply place a bungy cord from one arm to the other. This does a fairly adaquate job of keeping the arms from swinging and flopping around when there is not an implement attached. It really depends on how tight the bungy cord is. You won't be able to move the implement into place though as the bungy cord is simply not strong enough to hold the arms in place when pressure is put on them.
I have attached a picture for you.
If you have any other questions please don't hesitate to ask.
Jerome