Converted it both way with Magos' but no such luck, it seems the Translation program ruins the model somehow. I just set the size to 0.7 in all three axes in it, but something goes wrong. Here's the screenshot I've got after trying to open the .mdl after it was resized in the Translation editor:
Since that didn't work, try this:
1. Open your model in Magos' Model Editor
2. Go to Windows -> Global Sequence Manager
3. Right click anywhere and select 'Create New'
4. Enter a duration. e.g. 1000 and click OK
5. Go to Windows -> Node manager
6. Create a new root bone, and put all existing top-hierarchy bones under that "root" bone. You do that by selecting move left/right from the right click menu. You need to have only one "root" bone on the top of the skeleton hierarchy.
7. Right click that "root" bone and click Edit Node. Click on Scaling. You will see a window with text like this "0: { 1,1,1 }"
If you had worked with GeosetAnims before, then you would know what the text represents. However if you had not, 0 = the frame number while {1,1,1} represents the {X,Y,Z} scaling.
8. Now you will edit it into:
"0: {0.7, 0.7, 0.7}
1000: {0.7, 0.7, 0.7}" (no quotes, and 0.7 scale since it's what you originally wanted)
9. Set the Global Sequence ID to the one that you added in step 4.
10. Now the mesh will be scaled to 70% of it's original size and bones will also scale accordingly, so animation is not messed up.