man i aint no expert like some of the dudes on this forum, but i have two blue gouramis about 3 - 3.5 inches long and i recently added two albino tiger oscars about half the size.
at first they where kinda scared of the blue gouramis, but about 2 days later they where takin food out of the gouramis mouths and fighting for food. i had to practically scare the oscars into one corner to get some food to the gouramis.
now the oscars are about the same size if not a little bigger then the gouramis and they chase them round but its different....like they swim really casually up to the gouramis and the gouramis sort of realise that they are commin and swim off...its never really violent or fast, and ive never seen them really fight or bit eachother except for when feeding, and even then its not bad at all. ive seen far far worse aggresion.
i might just be lucky. having the gourmis in the tank first and then introducting the oscars later on i think helped.
who knows i mite run into probs when the oscars get bigger but at the moment they are awesome together.
and how luckys this, i got two blue gouramis and they turned out to be male and female (perfect pair), then i got two hoplo cats same thing (male and female pair), then i got two oscars (male and female).
they all just stick in their pairs and sort of do their own thing.
sorry for the long post. hope some of it helps.
matt.