There are two ways to dither VST32 from 24 bits to 20 bits. The first is to just play the 24 bit files into the Adat. This will result in possible truncation of the extra 4 bits, which will result in some audio loss. The other method, more robust, is to use the Apogee dithering built-in to Cubase VST32 to dither the 24 bit signal down to 16 bits and then record them on the Adats. This is a better method because the signal will not be truncated, and the Apogee dithering is supposed to dither down to 16 bits while retaining almost the dynamic range of a 20 bit signal, so the audio quality lost will be unnoticable.