So I was designing some Magical Things characters (mainly because of this thread, which ended in thoughts about how to turn your lab into your familiar), and then I found what's going to be my most hated rule in RoP:M. That one who limitates Magic Thing's Might because of their size.
The first time I read it I found it quite disturbing, because everywhere else you can have mighty creatures of small size, but I moved on and pretty much forgot that. But now that I'm back there with my lets-go-design-characters trousers on, I got stuck on the first step. Ok, size limitates might... but what are the sizes of things? Is there any list, anywhere, of things' sizes?
In cause there isn't, I'd been trying to figure something. I know that the basics rules for creature sizes are mainly two: one size steps increases or decreases mass for a factor of 2, and 3 steps does so by a factor of 10.
So, ignoring silly things like density, would it be ok to figure that a sword is something of Size -4 (because it's roughly about 3.4 - 5 kg, so about 1/20 of a human, and thus a magic item sword could have by itself might up to 5)? Or shoud I don't ignore density, and take into account that iron is about 8 times heavier than flesh, and thus if an iron human would have a mass of around 600 kg, swords should be even smaller, around size -7 (and so might up to 4)?
And what about rings? What size is a ring? Gold rings seem to weight around 5 ounces or 140 grams, so size -8, ignoring density, or something as low as around -11, not ignoring it (and might not higher than 3)?
On the big sized things, what would a lab size be? Stellatus' description in the core book says that he's small for a dragon (though at size +8 it's pretty much in the average of other books' dragons, but whatever) but still bigger than most houses, so a average house would be of size 6-7, and thus maybe labs, being big rooms, would probably be at least 4 and probably up to 6, if we consider that labs are large rooms and probably houses where pretty small back then...
So I'm lost in an ocean of sizes and weights. Does any of this seems coherent, or anyone knows of a beautiful items sizes table I forgot about? Or should I just forgot that rule and assign magic might to Magic Items like it's done for any other magical creature?