There are a few options:
(1) Set the model for the dummy and then use that dummy with an altered scaling. (this option is kind of ruled out if you are using Dirac's system though)
(2) There is a field in the object editor that affects scaling, iirc. It will be under required animation names or something similar. You can try inputting "Large" for it. (I believe the ogre has this, so check that object and see which field has that)
(3) Rescale the model. You can rescale the mesh very easily with Magos' editor, just go to Window -> Model Editor. Drag select all of the vertices so they become green, and then go to Transformations -> Scaling. Scale it up a little (1 = 100% of current size, 2 = 200% of current size, etc. you can have decimals too). Then just use that model instead. Scaling particle emitters are done a bit differently. You'll have to edit those in the node manager, and try modifying the width/length field (not sure about this, I don't quite remember).