I'm needing to find out about baggage allowance. I am flying from Texas to Newfoundland the end of March for 8 days. I have the standard roll-about to put (I assume) into the overhead.

But, I want to take a duffle bag. Dimensions listed for a 2nd personal carry-on is 17x13x6. My duffle bag is 20x10x11. If I don't pack it full, to where it is still 'squishable' to fit under the seat, will I be allowed to carry it on or would I have to check either the roll-about or the duffle?

American Airlines lets you check one bag free but Air Canada charges $25 each way for one bag and I'm really trying to avoid having any checked baggage.

Thank you, in advance, for any help anyone can give me.