Although I haven't looked lately, I don't think I have any problems with my 2006 2551. It bothers me to hear of the problem in brand new units, as it usually occurs in older installations when the thin plastic foam backing starts to fall apart from oxidation and heat exposure. In those cases you usually cannot make them look OK by just gluing them down, as you have grainy lumps showing through. This is the one drawback to buying direct from the factory rather than a local dealer. If this happened to your car, YOU wouldn't be slitting, spraying, and gluing - the dealer would. However, the price advantage of right from the factory built to order probably makes up for it.
Jerry