What I take from this conversation is that:
When tracking, try to achieve the -12 dB level. I wish you could monitor this from Sonar, but I was under the impression you can't, and I don't have any other way to monitor it, other than on my interface...which does not necessarily align with Sonar, in terms of metering or accurate levels. I think more experimentation is needed to find that sweet spot. Track then play back and check levels...adjust...track then play back and check levels...repeat!
Otherwise you must use a combination of gain and then volume faders to bring the levels down. I have found that this approach requires much adjustment and it kinda makes me feel uncomfortable, as if I am doing something wrong.
When I first started I used to use to track HOT. Then I made the adjustment to reduce those levels, based on good information in this forum, and I was successful, but it sounds like I have to reduce those incoming levels just a little more. -12 dB is not a hard number...I mean -9 would be acceptable too. I am just trying to give myself room for mastering.
It is all still new so it is a journey. After all I work full time and this is a hobby...I miss days or even weeks from sitting in front of Sonar. So it's always one step forward and two back.