My wife reported some truck and cross-wind buffeting on her Seoul Train when we first got the car. It was nothing like as bad as what one used to experience in rear-engine VW Bugs and Chevy Corvairs, but it still was there. She chalked it up to the light weight and boxiness of the Soul.
Then we had an SSD strut-tower bar installed. Among all the other benefits of the strut-tower bar, the buffeting problem almost disappeared. It's now no worse than she got with her VW Jetta wagon.