In my limited experience, I'd say agitated psych pts are handled very well. I have nothing but admiration for the security in the ED. Of anyone involved in healthcare, Drs, nurses, paramedics, they more than any other seem to be able to say, "They're sick, its not their fault".
I'm passionate about (and involved in) mental health advocacy and least restrictive means and all that, and to be honest I'd be strapping/drugging a lot more people down than they do.
We have four point padded restraints on all the trucks. Put them on and hide them under a towel if you think you'll need them. Problem is, esp with some fire in their belly, the pt can sit up/head but/bite. I've heard that moving one of the arm restraints up over the head so that one arm is restrained down near the hip and the other above the head prevents this nicely. Apparently there is some issue (pain or discomfort or some rubbish). I've tried it and I didn't think it put me in any unreasonable discomfort. I'd be happy to use it and just keep a good eye on the pt. At the end of the day, if they dislocate a shoulder or similar its easy fixed and its better than them dislocating my face then jumping out of the ambulance on the freeway.
P2 mask over the face for spitting pts.
I have some personal insight in mental health problems (good for building bridges) and received some pretty good education in de-escalation, which is a bloody good thing because I sure don't have any muscle to hide behind. I do wish we had more options for chemical restraint.