Would it be ok to mount a QS8 with the full metal ceiling mount to a ceiling by screwing into the strapping instead of the joist?

As long as the screws have a good bite into that strapping it will be fine.

thanks for the quick response jakewash! I am really excited to hear the qs8's for the first time, but have been reluctant to mount them, the other is going on a wall so that should be no problem, as long as I can find something at the hardware store to do it, these are used v2's and the seller for some reason didn't have the free mounting hardware that came with the speakers, i did buy the full metal bracket for the ceiling, but i dont really want the wall version for the other one