I dont understand your problem, My airowear can be adjusted independently lower and higher, It has two independent fastenings, one at bust level and one by the lower ribs.
You also adjust the top of the shoulders to fix the level at which it hangs.
Mine is L3 short Airowear Outline.
I am between sizes and after trying many bps, I decided to stay with the size I have always worn which is slightly too small, leaving a gap down my sides. But as I dont compete in it, that doesnt matter.
I believe that Airowear were taken over by Champion and when we last drove to the Equestrian store, I decided not to upgrade and replace my old bp as I feared the new one was longer and would catch on the saddle.