How would you do it?

yes I would

It really depends on what type of game you are playing. Is it 300 points, 400 maybe 500? I'll assume that it is a stock 400 point unrestricted tournament. There are several things Terrax has going for him. First, he has very good range plus Running Shot. Second, he has a nice 12 attack (especially useful now with all of the 19+ defenses). Finally, he does that nasty 17-16-17-16-17-16 trick with his defense value, which throws many an opponent for a loop. His drawbacks are two-fold. First, he lacks the big damages values many figures at his point cost have. Second, (this goes along the first) he is dependant on BCF for maximum damage dealing potential, which is not that great on a 172 point fig. That being said, Terrax can be dangerous if used properly. Have him carry an Enhancer (such as The Red Hood), use the ICWO feat on him and suddenly he is dealing out 5 solid clicks with a 12 attack from 10 spaces away. Park him on some hindering and make your opponent come to you. Then you can either use his Ax (BCF) or go for straight damage. I know there are other figures who may do the same things better and for less points, but the question was how to make Terrax work, not "Thor could do that for less..." Terrax can be dangerous if his fellow teammates compliment him well and if he is played properly.

I don't recommend ICWO on many figures, just b/c its overused, but Terrax could really use such a boost for his damage.

What sublime said.
I've played against him and his strategy is rock solid.
Although I haven't seen him around here lately (I think he when into hiding in the Southwest U.S. somewhere...location unknown)

@sublime: Come back and take your beating sucka!