I am also unable to get midi tracks to play using VSTi(s). I am using style J~LAURA, which has midi Bass, Piano Guitar and Strings... The real drums are playing...I added the following three VSTi(s)

Kontakt 5 upright bass in first slot for bass using channel 2
Absynth 5 plucked strings in first slot for guitar using channel 7
Kontakt 5 session strings in first slot for strings using channel 6

I did not add a piano synth...I unchecked USE VST/DXi Synth in the MIDI/AUDIO Drivers Setup, because when it's checked, the plugins button is unavailable in the mixer window...I don't see any midi activity coming out of BIAB into the VSTi(s)... also, when I save the song I get yellow box with message VST/FX data too large to save, size is 1,447,873, track is 4...