I put a QAD ultra rest on my alleginace this year and it is a great rest. It is a drop away that you can cock at the full upright position and it also has a bar crossing over the prongs so it also has the full containment feature you are looking for.

You don't have to cock it every time you shoot it. It will finction just like any other drop away rest out there while practicing but in the treestand or stalking you can cock it to keep your arrow on the rest.

So far I am very happy shooting it during my practice sessions. I have tried to get the rrest to uncock by "accident" but to no avail. It works just like they say.

Check it out here.
http://www.qadinc.com/ultra-rest.htm