5psi seems very low, have you tried adjusting it in small increments at a time and testing it each time instead of just all the way in and all the way out?
And my second comment was not stereo typing you, it was part truth, sales people will tell you what you want to hear to get you to buy something, thats why we have these forums, find out who else owns one and see what it can actually do and how well it does it, as you said it will go down to 5psi but its a dog, but it was mainly a joke.
Only suggestion i can offer is to adjust it in small increments and test each time, as zennon said, will sit on 9-10 psi easily and that would be a safe boost level.