You don't need to go through hell and back to make sure everything is hitting precisely 0vu dude... First off, VU meters measure the RMS signal not the peak. Peak meters usually come in digital or LED formats on consoles. So the point is to set up your gain staging like you would in a console/ tape machine, with most signals averaging around 0db. The Slate VCC meter is going to show you the RMS, just like an old console would. Your drums for example will be peaking closer to -10 to -6ish. This is perfectly fine and normal. When I set levels of drums to tape with vu meters, they frequently DO NOT go near 0VU. This is because the peaks are too fast for the vu meter to read, and will end up distorting/ clipping if you try to push them too hard.
Don't go too crazy. If you're tracking the stuff, just record with your meters mostly in the green. Your drums will peak a bit higher, but try to keep them below -6 for the most part. If you're mixing stuff that you didn't track, just trim the input a bit til it's at an acceptable level. I do like the VCC meters a lot, so I just keep the master buss meter open, solo the track, adjust its trim real quick, and move on.
Anyway just keep this in mind: you're aiming for -18 RMS, or 0VU on the slate meter, and it's not life and death. Just leave yourself a little headroom and mix some shit.
