I have watched one too many videos with the effects of an inappropriate carseat for weight/height. It is simply heartbreaking. I can tell you to do the research, look at what the non-seat manufacturers sites tell you, and go with that. I do remember using a 'noodle' to safely install the travel system seat. I had it checked by TWO certified inspectors (after being told by a new mother AND a police officer (who had a child himself) that it was correctly installed). If they haven't sat through the 40 hour course- they don't know what they are talking about.
I'm with you on the safety. I was in a bad car accident with Ty when he was only 2 months old. Scariest day of my life. My car was totaled, I was sore and bruised, but Ty was perfectly fine thanks to a properly installed car seat. Always better to be safe!