I used to get the same issue in Modo. I personally like to fix the model scale in NetFabb once I've exported it to STL so that my source file (Modo) is left intact. Whilst I'm fixing the scale, I also check the mesh is watertight etc... in netFabb
Netfabb is free but you can access additional tools if you upgrade to their professional version (I'm not using a professional version however). All the free tools generally covers what you need (checks the mesh is water tight, can fix scale etc...).
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