Some years ago I had a go-round with American Airlines (domestic) on carry-on policy (this relating to forced gate-checking of the normal carry-on allowance on smaller planes). It got me to find and read the transport rule on which American bases it's rules; the transport rule that I found only said that airlines must decide and consistently enforce some rule that meets overall cabin safety needs; it didn't in fact specify any particular size or quantity of cabin baggage.
So, could you quote or reference the specific TSA rule, please?
thanks,