When i first went to Portland i found this to be an issue, but taking the yak of the car while at camp allowed it to go back to normal, however it wasn't that hot on the trips down or back but from then on every time i use my roof racks i just put 75mm pvc under the yak that sit in the channels of the PA, this has certainly made a big difference with no deformation now and confident to carry my yak like that for several hours travel