After the arrival of Reforged, RMS was updated and incorporated a lot of new stuff. Scaling up the model is no longer a painful job like in MdlVis.
Using RMS-Retera's ModelStudio, you can easily do this in less than 30 seconds.
Download the latest version of it:
This is Retera's Model Studio v0.04 Public Beta. It is not finished! But it is something that works and is better than the Matrix Eater application, and is compatible with Patch 1.32. Retera's Model Studio is the second evolution of the Matrix Eater project. It is a standalone MDL and MDX model...
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Open the model and select "all" Geosets and Bones referring to its skeleton structure, use "Scaling" to the size you want, reposition the model, moving it to the correct position on the X, Y and Z axes. And everything is ready.
ps. Typically for original campaigns, the template will have the default look built into the .MDX. Maybe in a custom campaign you can change it through the Editor or using Triggers.