Invisalign and Palate Expander in Adults?

You are right.  Your question shows a high degree of sophistication.  A Saggital Expansion Appliance can help to correct a mid-face deficiency.  Orthodontists with traditional training have been incorrectly taught that surgery is necessary to change bone structures in an adult.  If you look at my cases shown on this site, you will see examples of adults that had midface corrections without surgery.  You need to find an orthodontist that has a good deal of experience in using Functional Facial Orthopedics or you will become  frustrated talking with more traditional orthodontists.  Good luck.

I am impressed with your knowledge of orthodontics and dentofacial orthopedics.

You are in an unique place in your life and skeletal developement. You probably have not had your last little "growth spurt." The appliances you are referring to have had good success in growing children but are not much use in an individual whose boney sutures have fused. The problem is knowing if you are an early developing or a late developing 20 year old.

Other than case reports, I have not seen anything in the research of the dental literature that shows that you will get any mid face coerrction in an adult without orthognathic surgery.

Your case touches on a very hotly debated concept in Orthodontics. When is one too old to expand bone without tipping teeth. My father who practiced orhtodonticts for over 30 yrs felt shortly after puberty was about the limit, yet found in select older case he had success. Myself , in practice for approx 11 yrs, with many other Orthopedic Orthodontists, now believe you can get true bony changes without surgery much later in life, even into your 50's. Do we feel you get the same results no. Surgery has limitations too, but different than orthopedic movement.

You clearly have already seen changes, trust what you see. At age 20, I agree it is likely you can get more our of your expander. Don't be afraid of your doc flaring the anterior(front) teeth a few helpful degrees UNLESS you feel they are already flared.

In my experience the expanders would do much of anything to your zygomatic arch are which is a contributor to your mid face deficiency. Surgery or fillers are needed for that.

Neat case. Continue to work with your doctor and educate yourself.

Neither an expander or a sagittal is changing your bone structure as an adult.  Both appliances are simply tipping your teeth, just in different directions.  As an adult only surgery can change your bone structure