You're scared of the aggression and biting - They can sense this, and they will take full advantage of this.
I can add my experience with our Meyers for perspective. Remember, a Meyers is about a tenth of the size of a larger 'too - maybe less than that. I am 45 years old and have had birds since I was a teenager - including a few years with an wild-caught Umbrella. I feel I have a pretty good amount of bird experience, not as a breeder, but as a dedicated owner of many wonderful companions over the years. I've read MANY books, articles, watched videos, attended bird seminars, etc.
In 1995, we had a quaker who was quite attached to me and my wife felt a bit left out, so she wanted a second bird. We found Cleo and arranged to meet the breeder which ultimately led to us bringing her home. Cleo formed a great bond with my wife and also tolerated me - no signs of aggression whatsoever. One day, Cleo walked across the floor to me as I was sitting at the dining room table. She climbed up my pant leg, up my sleeve and onto my shoulder....not at all out the norm. She sat there and innocently preened for a bit, got some scritches from me, and then for "no apparent reason" (I know there
was a reason, but didn't recognize it at the time) she attacked the back of my neck and ears. She cleverly placed herself behind my head down my back a bit just out of my reach. I called out to my wife who came and got her off of me, but the damage had been done...I had many bite marks and deep punctures on my neck and ears, and it was quite bloody. Didn't need stitches, but did develop some significant bruising and recovery was quite painful. This was in the fall of 1997.
To this day, I cannot trust her (I mean **I** cannot trust her...not that she isn't sweet, it is in
my head). I move her around the house on a perch, and do allow her on my knee only (but I do create some sort of barrier to prohibit her from running up my shirt to my head), and I do give her scritches on the top of her head - but not to the extent I used to be able to do. My wife handles her easily, and Cleo spends hours sitting on her getting doted on. The only time I am not fearful of her is in strange places - e.g. vet - where I am her familiar person.
I have, in my opinion, alot of bird keeping experience, and I know the "tricks of the trade" - target training, gaining trust, etc. But I still have innate fear of her that I know she senses and uses to try to manipulate me. I can't train
myself to get over it. When she flutters onto the floor near me, I am fearful that she is going to go after my feet.....even though she rarely does that. That attack from 16 years ago
still controls me, and I've been unsuccessful in overcoming it. I have, instead, learned ways that I can enjoy Cleo, and still have a relationship with her. I can handle any other bird, no problem, just not my sweet Cleo. I still love her very much.
My point is that you need to also consider how YOU are going to be able to deal with the inevitable. It is not easy, and not always entirely something you can control, no matter how well prepared or how much experience you believe you have.