I use a 7.1 avr with a 9.2 setup to take advantage of the various formats and not have to make that compromise of Front Heights or rears. I don't think putting the rears up high will get Front Height signal due to processing in the pre-amp. Even though the Height channel are a matrix since there are so few BD with PLIIz material. If I had to choose, I would rather have Front Height over the rears since the front stage is more important. Nine speakers is not practical for many rooms and a good 5.1 or 7.1 setup will be adequate and you will not feeling that you are missing anything. In my setup only 7 speaker can work while whatching a BD or TV.
Klipsch RF 7 based HT 7.4, Pioneer SC 35, Acurus Five 200 amp, Chase SS 18.2(2), VS 18.1(2), Samsung BDP F 7500, Asus/My Book Live HPC 4 TB
Yaquin VK 2100 amp, McIntosh XR 5 speakers, Samsung BDP F 7500