<set_object_property property="size" value="10.0" name="Monster" />
<set_object_property property="maxHealth" value="3000" name="Monster" />
<set_object_property property="health" value="3000" name="Monster" />

And I've discovered that it looks like not all monsters can be re-sized. 

Typhon: No.
Whale: Yes.
Shark: Yes.
Dragon: Yes.
Pirahna: No.
Charybdis: No.
NSect: No.
Jelly: Yes.
Wreck: No.

I'm not sure exactly if there's an upper limit to the size... it's a float value, so the upper limit would be arbitrarily high. Once you get above size 300-ish or so, the size of the creature can be larger than the draw distance for the viewscreen, so your ship could be "inside" the monster but still be too far away for the engine to "draw" it on the viewscreen. 

The other quirk I've noticed is the "pushRadius" (or whatever it is monsters use for collision) does not change. So a normal-sized ship will clip inside a size 30 shark or dragon before the creature gets close enough to perform its attack routine. Likewise, you can fly right through a size 30 jelly and not collide with it. I suppose if you wanted to prevent this, you could set-position a hidden mesh on the monster with an appropriate push radius, but this wouldn't quite work for non-spherical monsters (and might interfere with their physical attacks). 

I was curious if anyone else has been playing around with monster sizes? I haven't played around with speed or turnRate yet. Have you run into any other quirks?