[bivenator]

All parties in my custody dispute were required to have a psych eval. Not sure if this is similar to a custody evaluation as you used both terms. The psych eval. was a series of personality tests and finally and observation period. The psych went behind a one way mirror and observed my 2nd wife, daughter and I as we played board games for 45 minutes. We were also interviewed by the psychiatrist.
My opinion of the psych eval in my situation was that it was completely useless and an entire waste of time.
My ex wife came back with some flags in the personality test but the psych did not want to recommend that custody be given to me so as to retain the "normal" routine that the child had established. My 2nd wife and I checked out fine.
We did not get custody at that time. My daughter was 10 at the time and by age 12 she had come to live with me full time.
The psych eval that was performed somehow failed to predict that my ex would flake out and my in laws (who the ex was living with) would slide into full blown alcoholics.
Psych eval IMHO are a waste of time and money.
I sincerely wish you the best of luck.