Exactly! I watched the 3 hour "Making of Aliens" documentary the other day and I'm the same as you. In fact, even though I already knew, the most detailed Aliens were the puppets they used. But that's what I love about the Xeno; it allows for TONS of licence to be taken. You can change a lot to make it fit in with what you need, yet it's STILL recognisable as a Xeno!
Good luck with your build, I'd be very curious to see progress!! Hopefully you'll learn from some of my mistakes!!
In fact, I stopped getting hung up on accuracy very early on in the project. The ONLY thing I'd change and I'm not happy with is the head. While it's the correct length, I made the jaw too long and so the whole thing sits forward too much and makes the whole thing look shorter than it is. I'd also make the "helmet" part differently so I had a shorter neck. But I'm buggered if I'm changing that now!