Front Wide speaker setup. Do I choose 7.1 or 5.1?

I have a pioneer receiver that allows Dolby IIz front wide speaker configuration (2 left and right channels to the sides of existing L/R channels). Now I'm wondering if I need to setup my audio output to 7.1 from 5.1. The issue is 7.1 is usually reserved for rear surrounds (which I don't have). I have a center, left, right, wide left, wide right, side surround left, side surround right. Yes there are 7 channels, but there are no rear back channels.

It's 7.1.....and here is more info on it- Dolby Pro Logic IIz Details.....

If you don't have 3-ft of space behind your seat, front height or wide is a better way to go....