I did almost the same last summer but went in via Piute Pass. I had gotten the entry permit 6 months out but was unable to the Trail Crest exit at that time. I came into Lone Pine a day early and was able to get both a entry and TC exit permit at the ranger station in Lone Pine. I believe you cant get a TC addon to your original permit. You must start over getting a new permit if the exit is available at that time. From the beta I have gathered mid week is the best time.
Edited by pcieluch (02/11/19 10:59 AM)