The first thing you have to understand is that the VU meter is showing you rms levels mainly.
(peak meters respond to the loudest fastest peaks, rms meters are showing the average level or the meat of the sound essentially) When you say you are setting the VU for -12 on the master stereo buss and the meter is OK there, the track meters are low. What track meters are you talking about.
The idea is you insert another VU meter set for -12 on the tracks as well and you see them swinging up to
0 dB VU as well. You can insert as many VU meters as you like anywhere in your signal flow.
You cannot use existing DAW meters to show rms for several reasons.
1 Usually they will be showing right down on the scale. Not so useful. And not as useful as a meter that comes right up to 0 dB VU.
2 Sonar shows rms readings 3db lower than they should because they are showing actual rms readings which are 3 db down from peak.
So the idea is you use the VU meters (Klanghelm) on tracks, busses and the main stereo buss. Everywhere. Also -12 is a little hot for general project levels. It should either be -14, -18 or better still -20.
Use your existing DAW meters in peak mode only to keep an eye on very transient material which won't move the VU meter much but the DAW peak meters will keep you informed then most of the time. The idea is to watch how all your levels are VU wise mainly and let the peaks take care of themselves.
(they will because there is lots of headroom above that rms ref level or there should be. Another reason why -12 is not so good in projects. You are only allowing 12 dB of headroom which is not a lot.) When you start using the VU's correctly you will find your tracks will just reach 0 dB VU and the track fader will be around unity. The same applies for busses and the main stereo buss. Leave the main stereo buss fader alone at unity but you will find you will get your mixes right on busses with the track faders all being around unity where you actually have the most control and the best fader range of movement. It is also OK to fine tune buss levels. That is what the buss faders are for!
eg say you have 4 electric guitars on 4 tracks and each track is showing a nice 0 dB VU. That means they have all been tracked correctly. If you send those 4 tracks to a buss you will only have to pull all four of them down not by much
(close to unity eg -2 or -3 dB) to get the right balance and level on the buss they are all going to.