We have toppers on our 5th wheel's slides and have had them open in some pretty severe winds and heavy rain with no problems so far.
However, when a tornado warning was issued while we were at Dobbins ARB, GA, we pulled the slides in before we evacuated to the shelters.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW