I have seen this question asked before and a search might prove more helpful comments.
I do recall that while the ladder is "good" for 225 pounds of user climbing it for maintenance, the Kayak sticking into the airstream will put drag induced weight where you do not want it; PULLING the ladder from the wall.
This puts maximum stress on the screw threads and the sealant at the roof and top of the wall. The wall itself is providing almost no support to this "extra weight."
I think the short answer was "bad idea."
Perhaps a "roof mount" of some kind streamlined into the wind would put less stress on the roof material. Watch your height increase, though.
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