Brett and his associates don’t talk much about your mouth or your soft palate, but take a look at him here. http://www.youtube.com/watch?v=Lx-BpQFbLrg
Do you see his teeth and the wide smile? I love this! This is exactly the placement for singing high notes, regardless of the style (unless you are singing opera or classical). This wide smile and lifted upper mouth allows the vowels to resonate cleanly and nicely in the head voice.
Also, note the sob (moan), and “cry” to his voice. This is essential for good vocal cord closure.
Try it! Don’t sing too loud. Just allow those high notes to blend with the low ones, and VOILA!