If you use a female mmd or xnalara model I guarantee that your feet trackers will not match the feet of your character. Half the time a female model wears high heels and the other half of the time the model has super long legs because long legs are ideal feminine features and are exaggerated in models.
VR chat and by extension steam vr sets your floor height based on how high your head is off the ground, but it also expects your arms to be a certain length based on how tall you are. If the game knows you are 6 feet tall and it knows that your hands are about 3 feet from your head, then it expects your feet to be 3 feet lower, but what if your model’s legs were actually 4 feet long when scaled properly? You would be crouching in game, so rather than having crouching avatars, they just make the in game floor lower than your actual floor.
The only way to fix this issue is to shorten your models legs and leg bones in blender or some other rig editor. I shortened the legs of one mmd model and after making them 60% as long I could finally touch the floor in game. Cartoon avatars are not anatomically correct, so you just need to except that you need pc users or lolis to pick things up for you. Or you could just make a really short model.
btw, you don’t actually need to have shorter legs on an mmd model to use kinect tracking. I just put the balls in my model’s calves and it works pretty well.