May be because I'm using a five-year-old version of desktop free SketchUp rather than their "pro" and/or web-based versions, but:
When I use their exporter to create an STL from my model, then import that into S3D, the latter sees it as TINY -- the data's all there but it's postage-stamp sized even if I let S3D "fix" the units. I wind up having to go into the model description and readjust the scale myself, usually by a multiplier of more than 9000. (Having done that I can export the STL to "save" that change, but I have to redo it every time I tweak the model.)
I presume this is SketchUp's fault rather than S3D's... but if anyone happens to know how to persuade SketchUp 2017 to Play Nice With Others, that would be great. Or if there's any way S3D could recognize this particular goof and offer the correct scaling automagically, that would be Nice To Have.