I question the reference to scale here. I know for a fact that the Powerloader was partly worked by having a large man inside of it, and that Sigourney Weaver actually sort of sat on his lap area, as it were, so the crew would play jokes on her and put stuff where the guy's crotch would be, so she would think "something funny"
was going on behind her.
My point being, if the PL was that much larger, a man and Sig wouldn't be able to work in tandem within the parts. I think it's scaled pretty closely.
It looks larger on film due to the fact that camera angles and low positioning, made it look much larger in the viewer's minds eye.
Look at the dimensions. She is standing almost three feet off the floor, scalewise, on our PLs. That is about right.
When I held that piece of the grip claw at Bob Burns house, it was about the size of the one on the toy, scalewise.
The belts, rollcage, and other parts, are about right to my eye.
And remember, Sigourney is 6 feet tall. Taller than many men. That makes her large in that rig, as she was. Again, scale.
The arms can't navigate too far out of her reach, again, scale.
Much larger and it would have been too cumbersome even as a prop.
The antenna on top only were there to serve as camoflauge for the two wires that were attached to a crane rig that held the whole thing up in the first place.
So, other than being proven wrong by seeing a good shot of this side by side with the actual one from the movie, (Calling WorGar!) I believe it is close.
That's just my humble Op.
One more point: Again, at Bob Burns, the Queen's head, the actual one used in ALIENS, which I have seen and touched, was actually, dare I say this, SMALLER than I would have thought. It is huge yes, but not as large as I imagined. Camera angles do amazing things! Think about that.
ADDED:
Look at these two shots:
Mine
The real one:
Mannequin's odd, and VERY skinny, and the pose of the real PL is strange and awkward, but the dimensions look about the same to me. If anything, the real one looks thinner in some ways.