I over looked some of the details, but yes, 1.5'' thick foam is pretty much unheard of, definitely a no-no... an inch is about the maximum thickness you would ever want to go for all overall construction, but like Muppetlab says, half inch would work well too. From experience, I've traditionally used inch-thick foam strictly for skulls and jaws, but I've learned that that usually only works well with puppets that have stiff mouths, if you want a more flexible mouth, then half inch foam is the way to go.
Another tidbit too, the fabric you're using could also play a factor as well: the higher quality the fabric, the thicker and heavier it's going to be, I've learned that the hard way. If you look at my work, the two forefront characters of my universe are monsters. Steve D'Monster is pretty much covered in shaggy fur from head to toe, but the fabric is low quality that came from a throw pillow, and as a puppet, he's mostly very lightweight and easy to manipulate; Bethany Crystal has what I call a "poodle cut" to her fur design, but her fur fabric came directly from an online source, it's much higher quality, and as a result, as a puppet, she's rather heavy and somewhat cumbersome, making her more difficult to manipulate.
I know most puppet builders always insist on getting the best, top-notch fabric for everything, ranging from fleeces to furs, but sometimes, the better the quality of the fabric doesn't ensure a more free and flexible puppet. I know everybody insists on going through measures to obtain antron fleece, I'm perfectly happy with polar, blizzard, and even polyester fleeces - they all have worked very well with me, and I honestly don't care about seams showing, and I don't believe people watching care either, sometimes they seem to actually look for things like seams, rods, strings, etc.