Hi,
Could you share the file? I'd be interested to see how you are going about creating the elevation.
What I think may be happening is the exported 1:200 elevation have a different resolution than the rendering. Have you tried just exporting the un-scaled scene from SketchUp at the same pixel resolution as the rendering and composite those two? Then you can re-scale the rendered elevation in Photoshop based on the 1:200 elevation you've already exported.
I think SketchUp takes some liberty when it exports a scaled drawing so there may be some discrepancy between the scaled view and the rendered view. Let me know what you come up with, and I'd love to see the final result. But again, if you still have trouble with it, post the scene here or send it to me directly, and I can give you some more direction on how to best solve this.