Well, KDS777, I took your advice and bought seats on GOL. The flight time was the most convenient for me, too.
My flight was slightly over 650 miles, so BA Avios wasn't so cheap. As you know, there are a lot of discounted fares in Brazil and, it would seem, they're easily available to foreign travelers (unlike, say, some airline/country policies in Chile, Argentina and Peru).
I have "Tariffa Light" -- I have a US credit card that offers travel credits, and they can only book the lowest fare (which is this class). Tariffa Light DOES seem to include carry-on: a normal sized suitcase at normal weight. Does anyone know if you can also take a USA-sized "personal item" along? The website is silent on this. Also, I'm wondering how strict they are with carry-on in general (like will they weigh my bag to make sure it's not over 10 kg?). Thanks.