I think the City Hunter's proportions were inspired by this promotional photo:
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As for the Jungle Hunter, he's not that chunky in person. The worst you can say about him is his proportions look normal rather than tall. The placement of the trophy necklaces in that collector's photo doesn't help either.
I'll admit Prime 1 could've stretched him out a tad more, but his body mass feels accurate. The Jungle Hunter suit isn't slender by any means, it's just that everything about it is big. In some shots he appears very heavy, like when he's roaring at Arnold or jumping along the rocks. In others, the proportions are a bit more elegant (but I think that particular side of the character is captured more in BTS photos than the actual film). I don't think Prime 1's statue evokes anything we never saw or felt on-screen, let's put it that way.
Having that said, I'd be curious to see these sculpts posed fully upright. Would they still appear squat or would they demonstrate the same dual personality the actual suits do?