Another thing to be careful with on Pipers

The top latch can have excessive vertical play.
It is possible for the top latch (on the door) to ride up over the top
of the catch (on the fuselage). After you takeoff, the top of the door
will pop out. The main latch on the side will hold, but it will be a
noisy, windy ride. Do not attempt to close in flight. Land, pull off
onto the taxiway, reduce throttle to minimum, then relatch.
With the door open a couple of inches, it may be necessary to gently
pull the top latch down with a finger so that it will correctly engage
the catch.