I flew an LS-3 for many years, which nominally has the same airfoils
as the PIK. When it was newer, I had some "falling out of the sky"
experiences, too, although not as dramatic as the PIK drivers
reported.

Slowing it down and using more positive flap than normal as suggested
by several PIK pilots seemed to help. I later kept my wings in a 400
grit sanded surface, and once for a few years at 220 (the latter was
very difficult to keep clean, the joke being that one had to sand off
the bugs!). The satin finish seemed to help substantially: the water
didn't bead up; it "sheeted" instead and flowed off. It still came
down faster than usual when it got wet but it wasn't scary and, as one
fellow suggested, sometimes it's difficult to separate the effects of
rain and storm-associated sink anyway.

Chip Bearden