Remember you get what you pay for. In seeking an IME it would suit you better if you got an opinion from a Specialist that is an Expert on your condition i.e. Heart = Cardiologist, Feet = Podiatrist and so on. Furthermore why would you need an exam for a current condition and current meaning "At the time of you filing your claim" and NOT during an office visit? In that case all you should have to do is get a copy of your Medical Records and send it to the Doctor for him to review, assess and formulate a well written IME.
Some of you may ask why NOT get a current exam and the answer is suppose you go to OKC and your condition has improved? I don't know anything about this Dr. Ellis, but the V.A. isn't stupid and sooner or later a Veteran who does not have a track record of seeing a Dr. for a condition will try and use a thinly pieced together IME via a single office visit in OKC and the house of cards will fall.
Good Luck and Semper Fi.