I agree with Curl. The character of International style Viennese does not allow for "syncopation". The essense of this dance is "uniformity" and "repetition". Not just for the individual couple but also for the entire "floor" as a whole, creating a chorus of synchronized whirling and twirling. Foot placement should take place on the beat.
However an important note is the timing of the actual musical beats (1,2,3). The time between 1 and 2 is slightly shorter than the time between 2 and 3 (authentic Viennese Waltz timing). In other words, all 3 beats are not evenly spaced apart. Beat 2 comes "ahead of time".
As one steps on 1, commence and continue the acceleration into 2. Then decelerate as you close smoothly on 3. Don't snatch 3 by rushing the closing of the feet on 3. The music will allow you to do this while still remaining "on the beat".
Regards,
Len.