Thanks for your reply, neuromancer. It looks like the best solution is to credit the Gol flights to FB (100% of the flown miles) and the TAM ones to IB, but basically because this month they're awarding 2x avios to TAM as a new member of OW, and M class gets 0,8 avios per mile.
I just hope those promo 2x avios will be credited automatically, because claiming them to IB later is such a PITA...
