Cliff, I believe you will eventually answer your own question on this one. If you are relatively new to overhead squats, you may need to improve on your hip and shoulder flexibility which, once improved, will result in a bottom position that is different from what it is now.
I
highly recommend doing overhead squats with a PVC pipe to build muscle memory and make this discovery for yourself, free from the load that you'll eventually use.
I believe the answer will be influenced by a couple of very important factors in my opinion. First, focus on maintaining what I call a "killer" lower back arch. And second, work on having a good upper body uprightness even though you will have some forward lean with an expanded chest like you are a big gorilla in the jungle. After these have been addressed, your depth and knee position will be what your body allows for where it is at with hip and shoulder flexibility.
I hope this semi-helps you at least.