Found an issue with "small" models.
Example: I'm importing a functional model that is 95x46x75.45mm in size. The STL is 75.45 tall, however, in order for it to import semi-properly, I have to use the 46mm as height.
However, the model, when imported, is actually 99.12x47.99x78.72mm in size, so it's actually 104.3261% of the original size in all directions.
If I import it at a factor of 100 (telling it that the STL is 4600mm in height), then downscale it to 0.01 in Sketchup, the size is correct.

@tig said:

Maybe it expects 53.69 but is receiving 53,69 - so does your system use a . or a , as the decimal separator ?
What do you actually type in the input-box ??
Also it seems to expect an integer, rather than a float in any case ???

I did type both 53.69 and 53,69 and both cause the error.
I ended up having to import it at 100x scale and scale it back down.. it's a workaround, but not really ideal.

Awesome plugin, but it doesn't seem able to handle decimals on the model sizes.. i.e. I have a model that is 53.69mm tall, when importing and entering that value, I get the following error, both with a comma and a decimal point: