Yes, persano designed this around the Kindle Fire HD 7" and is not intended to be used on the Kindle Fire HD 8.9" - due to several differences I would not recommend using this on the Kindle Fire HD 8.9" and the Kindle Fire 2.
This is a nice upgrade for the Kindle Fire HD 7". We will have modified build.prop for the others in our Kindle Fire First Aide. This feature will be available in about 2 - 3 months along with performance scripts designed for the Kindle Fire family of tablets.
need a tester that can modific all the values in mp9engine (very easy) to get the best in 8.9. because i cant see if it is fast or drain less battery because i dont have a 8.9