I have a Bavaria 36 with three sleeping cabins, and the boat used to be used for charter work. The boat was purchased in 2010 when it was already eight years old, and I suspect the covers had never ever been cleaned in the past. They were all taken off and washed on a very cool wash, and were then tumble dried until nearly dry but when my money ran out for using the marina launderette, and so were brought back onboard and were hung up over the guard rails to dry in the wind.
Re-fitting the covers was like wrestling several rounds with "Hulk Hogan," but I got there in the end and fortunately there was no shrinkage. They have been taken off again after the boat was removed from charter work and were brought home where I suspect either the wash cycle or the tumble drier was rather hotter than before and one of the covers has shrunk a little. This has resulted in the end of one of the bunk mattresses now curving up slightly. Despite that the cover has been under tension for a whole year since then, the cover remains a bit on the small side now, so take care with the heat of the wash.