Aside from the height and the fact that you needed a guy that had no problem staying in costume for hours on end, they wanted to put prostetic on him.
Some of you just don't get it, his build needed to have a quasi synthetic look in order to be part of Alien lore.
Anyhow, I can't bitch on the movie it's one of the very very few actual science fiction films that have been released in the last 20 years. You get one descent sci fi ever 5 years are so and a good one every 15.
Anyhows y'all need to know what real sci fi is