I'm sorry I wish I did. I am sure there are some YTers out there who know a lot more than I do. I just remember reading that a carrier should have a firm stable base with enough room for them to stand up, lay down & turn around in. I believe that the caution was about carrying them for too long in the upright position. I don't think it said not to use them at all. Sorry for muddying the waters. I really know nothing-just read this on the internet .
Donna
