Finally!
It took me 3 tries to realize how to properly use the bonus star + p switch to make a run on the 3rd area of the stage. However the p switch doesnt last long enough so I just felt to the lower area every time. You may want to make the path to take the star shorter, so we have more time on the p switch for the third area.
The area vs bowser gets too crowded at times, if the players are not clearing the floor with fire flower constantly, they will get overwhelmed pretty easily, bowser can push them towards the goombas hitboxes making them lose the Fire Flower, Bowser can sometimes block the path to the next fire flower making it even harder. Consider making a small pit so the goombas can die, that's the hardest part of the fight imo. You may even be able to add more pipes that spawn goombas if you add the small pit, so it's a constant stream of goomba instead of sometimes nothing, sometimes a pool of death.
That part is pretty doable without the star and the p switch, though! Just a little bonus. Where would you add the pits? I wanted the Bowser fight to involve all the mechanics in the stage-- belts, goomba spawners, and p switches. The fire flower gets shot to the middle, especially when you take the coins so it spawns even without the switch.