I am not sure if this helps but my previous 350 was a jdm, my current a uk. The jdm seats were much more comfortable and you sit lower, maybe it was just because you sit lower as they look the same. Whilst granted the cloth seats dont look as nice as leather, they would be cheap enough to try as a temp fix and if you like them, have them retrimmed in whatever you fancy. May be a cheaper route than trying something else to find out you dont like them either, worst case, you can sell the jdms back on for what you paid or there abouts.
I could be wrong but read the jdm seats sit lower because they dont have the electric motors, i dont know if this is the same for the convertibles.