Did it yesterday.
1. They were NOT letting H&V PPO sign up before breakfast, causing a few meltdowns at a Guest Relations CM.
2. We were at the gates at 8:15. When they opened up the far left queues for park entry, we were in first position at one of them.
3. We were let into the park at 8:45. We walked briskly to the Adventurer's Outpost, where a CM had people GET IN LINE. We were second in line. CMs hold signs directing the way.
4. We signed up for the 10:10 show in 30 seconds, basically. Got a free FP+ we were able to use for a second ride on Toy Story.
5. We then rode Star Tours twice before 9AM.
6. When we returned at 9:40 for our 10:10 show, the line was bananas. Late in the day they had a few stray spots for the 7:10 show, but they had closed the line at 9:30 and people waited an hour plus in line to sign up.
7. There was no way to "guarantee" fighting Vader over Seventh Sister. Yesterday, it happened basically based on height. The tall kids were herded to the upper platform, and the shorter kids to the lower. So if they handle it that way again, unless your kid is tall, he will get Seventh Sister.
I think with 7 they did it that way for PhotoPass, and it may also be that too many parents were trying to "ensure" Vader.
If you want to eat at H&V, do that, but know there's no guarantee of early signup.