With some libraries, especially older ones, raw samples may be shared between articulations. Accordingly, it's important to group like instruments so the RAM doesn't get soaked up more than once.
To implement that, load all the "sustained" violin sounds (legato, sus, vibrato etc.) into a single instance of Kontakt. Do the same for violin II, viola, etc. Assign each patch its own midi channel.
If patches don't share samples, it might not help, but it would have one additional benefit -- every instance of Kontakt is going to draw at least some resources.
Also, at the risk of stating the obvious, if you're using the library as a mobile sketch pad anyway, you can skip "extras" like violin II and Bartok pizz.
Finally, if you have an SSD, you can try reducing the preload buffer in Kontakt, but you may already have done that.
Good luck!
John