Michael Tully’s follow-up to 2011’s narratively erratic Septien is a coming of age comedy that’s mainstream in the extreme, which could work distinctly to its advantage. Accessible, amusing and sporting a soundtrack of 80s rap and soft rock tracks, Ping Pong Summer stands to attract attention from period-film fans and teens perhaps more attuned to their parents’ generation than their own. It’s the summer of 1985 and awkward 13-year-old Radford “Rad” Miracle (Marcello Conte) is on his way to the Maryland shore to vacation for a couple of weeks with his parents and wiseass, proto-goth older sister Michelle (Helena Seabrook)…