I have also used Thomastik Jazz Flats JF324 (?) Short Scale strings on my Mustang for some time. It might be the right choice if you want little tension, but they feel rather rubbery under the fingers. The E-string is also a bit thicker than usual (in comparison to the A-string, but also to other brands such as La Bella or Pyramid etc.). To me, the E felt super stiff and the A rather floppy at first, but I got used to it after a while. I have had Thomastik strings on my full scale basses for years (and they are, indeed, the best you can get for 34'' basses!), but I have to say that Labella's or perhaps even Dunlop flats (32”) are much better on the Mustang because of the gauge on this particular set. The jump from .70 to .106 is really noticable when you play.
Eventually, I switched to Labella’s Mustang strings and couldn’t be happier.