I'm pretty sure Bounce or mix to master track is still using the same 7/8 destination.
I usually bounce all rhythm instruments down first bounce, so in your case 1/1 + 2/1 + 3/1 + 4/1 + 7-8/1 to 7-8/2 (the number after the slash is the virtual track number-level).
Now you have tracks 1-4 ready for bass, a guitar lead and 2 vocals. Next mix/bounce would be:
1/2 + 2/2 + 3/2 + 4/2 + 5-6/1 + 7-8/2 to 7-8/3.
Of course the trick in this type of mixing is knowing how you want the individual instruments to sound in the final mix - before you have the final mix! I sometimes find myself going back to the original bounce-down and boosting up an instrument part, or changing the EQ on one, or some other change (more reverb, for example). There are techniques to this too - you get down to your final mix and realize the bass should have been louder, do another bounce mix, selecting the bass virtual track and the last bounce mix, and voila!