Originally Posted by mama2alexa
How safe/unsafe is it to use a custom cover (the ones for sale on ebay) for a Marathon?
Considering buying one as a backup, but dd want a girly print and the britax website doesn't have any.
Aftermarket products are discouraged because they MAY compromise safety. In some cases, specific information is known about unsafe products: For instance, the lap and shoulder belt "adjusters" (mighty tight type products) may actually interfere with proper lap and shoulder belt fit. Regarding a homemade seat cover, one concern is that the seat cover doen't meet federal standards for flammability. Beyond that, there may be some leeway for thin material.
It is best only to use the padding and inserts that come with the CRS or that the manufacturer sells for use with specific CRSs. Other acceptable padding includes:
a. Thin material that does not interfere with proper harness contact and fit.
b. No thick material behind the child or under the harness system.
c. No thick material under the child's bottom.
A thin seat cover or pad may not hinder the operation of a CRS but a thick pad, blanket or clothing may interfere with or reduce crash protection. This concern was generated by inserts of one inch or more of foam that began to appear in stores. The inserts that have a thin back (just to hold the side padding in place) are acceptable. However, extreme care must be taken to be sure that the insert has slots that do not interfere with the proper posistioning of the harness.