They actually switched it up again a few days ago.
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10am and 2pm are the new times—keep up with the blogs though in case it changes again.
As for strategy, I got boarding group #3 the other day by having the app open and clicking the Join button immediately at 10am. JUST MAKE SURE EVERYONE IS PROPERLY LINKED IN MY DISNEY EXPERIENCE BEFOREHAND AND BE READY TO QUICKLY TAP EVERYONE IN YOUR GROUP AFTER HITTING JOIN—that is the part of the process that normally slows people up I believe. Also make sure you have the very latest MDE app.
Judging by my experience that day though, be warned that Rise operations are still a mess. The ride opened late resulting in my boarding group not being called till around noon (despite being in group 3). When we were eventually called, there was a delay in loading while we waited in line followed by a total shutdown while we were on the ride—resulting in an evac from the escape pod elevator room. They gave us return passes, but when we went to ride later in the day, Rise was, again, down.
To Disney's credit though, despite the park closing like 20 minutes beforehand, DHS got Rise up and running and honored all previously uncalled boarding groups and exit passes from earlier in the day. In fact, they even let one family I saw enter the park after closing so they could use their boarding pass.
PS: Rise photos the mouse doesn't want you to see...
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(The screen looks so white because all the house lights were on—totally washing out the drop sequence screen.)