Asking for advice on mastering VSL Music on the VSL Forum is like asking for advice on skinning cats at a cat skinners convention.
Here's my .02 cents which is not quite worth two cents if you consider the current exchange rate but here goes...
Basically, all of the aforementioned advice from all of the aforementioned cat skinners responding to this thread is all good advice. In fact, it's all great advice👍 In double fact, there were things mentioned here that I found useful myself and I've been skinning cats for about twenty years now.
But here's my little contribution to this enlightening discussion. Pick one of your especially challenging tracks and master it to what you think it should sound like or at least as close to what you want it to be as possible. Then send that track to a professional mastering engineer who specializes or has experience mastering Classical music. When you get the finished product back, compare it to the master you made. Of course, you do this after you've been mastering some tracks for a while when you have some experience and you think you might be ready to go prime time with your mastering skills.
I did this about five years ago and I found that my masters were actually pretty darn good😊 However, if you were to keep score line by line the professionally mastered tracks were slightly better than mine. There were certain nuances that made certain frequencies shine and other subtle aspects that put the professional track above my own but only marginally.
Now in my case, 95% of what I do is library music for licensing and as far as mastering is concerned, "pretty darn good😊" is good enough. On the other hand, I regret not sending that 5% of scoring I do to a professional mastering engineer and that's what I do now.
Long story short, it depends on what you do with your music. In a perfect world hiring a mastering engineer to master your tracks is ideal but it may not be practical, nor necessary, in the real world.
Say... what is the current exchange rate on my .02 cents anyway?