I do have a MZX 300 keyboard and I have also converted STY to AC7 using the onboard SMF converter βΊοΈ but the thing is that it does not produce the accurate copy of the Yamaha styles.
Also it will be rather easy to have many rhythms as AC7 files on a flash drive and be ready to use on the go. For that, it would be wonderful if any software was available which could convert a batch of STY files to AC7. The onboard SMF converter can only convert one file at a time and also produces only lesser quality rhythms.π