Dolby Pro Logic IIz questions

[BigGuy219]

I was able to get a Onkyo HT-TC160 on sale and it's currently on the truck headed to me, and while I'm very excited ... I am also very nervous because this marks the first time I haven't simply gotten a basic $200 HTiB. There's a lot of features I'm not familiar with, and while I've done research there are a few questions I have about Dolby Pro Logic IIz.

I've downloaded the manual from the Onkyo website and looked at the connection diagrams and I've noticed there are an additional two speaker connections on the back of the unit, for "Zone 2" and the "height" feature.

From what I understand if I hook up 9 speakers to the unit, only 7 will function at the same time. I'm afraid the manual didn't seem to make it clear how exactly this works.

Some assumptions ... if I put in a 7.1 blu-ray ... the height speakers will be 'off' and the two rears will be 'on'? ... and if I put a 5.1 disc in and activate Pro Logic IIz the height speakers will be 'on' and the rears will be 'off'? Is it that simple?

Lastly, I've never liked Pro Logic on any of the setups I've had ... in fact, I've always used it only for mono/stereo sources when DD or DTS wasn't an option. When is Pro Logic IIz used ... for DD/DTS and stereo/mono only? Will it 'mess up' a lossless DTS-HD/DD-TrueHD/PCM?