We recommend that you use the pre-set proportions when you select the Manual Proportions option. The baseline inputs will cover 95% of users and allow you to really dial things in for your unique body shape over time.
Please note: if you notice that your legs are lifting off the ground when you bend over, the first step is to recalibrate your play space. The trackers base all of their measurements off of your headset height, and will result in abnormal movements if that data feed is incorrect.
We host weekly Calibration Support sessions on VRChat on Sundays at noon PST for anyone who needs a bit of help working through these steps. All are welcome to join!