sagging rotor blade

Patience, patience, patience.... 

It may take a few days for the glue to fully set if you used a little too much.  The best bet is to set them on a flat surface with a couple shims or blocks supporting the blades and leave them there for a few days to set up.  That should take care of the problem.

I've had the best luck using cloths pins to clamp the rotorhead where the grip joins the blade(s) while the glue drys. I normally let it set a few hours even when using liquid cement (my favorite). If the fit between the grip and the blade is a problem(and sometimes it is) it will cause a angle problem. I correct this by removing some plastic from the blade surface where it joins the grip, and then shimming to get the desired angle with sheet styrene.Another tidbit you might consider if displaying a flying model is coning of the blades. Same process as building droop into the blades for a static display, but in reverse to give a more correct look of "lift" to the model.   

Cheers,

Torq