Finished reading Rival Magic a few days ago and was going over the rules when I noticed a seemingly ambiguous section of text in the Muspelli chapter. "...each change in magnitude adds three to the Ease Factor of the effect". Therefore, my question is:
Is it possible to reduce a parameter when performing utiseta? If so, does this reduce the EF ala Hermetic Magic or increase it instead like with Amazonian Sorcery? I feel silly asking, but there don't seem to be any examples... 
I wouldn't reduce the EF; at the very least the EF should remain the same. It is debatable whether a Muspelli can reduce the spell parameters below those stated. Since Muspelli magic is based on Supernatural Abilities, it is much more restricted and less flexible than Hermetic magic. I must confess this is something which did not occur whilst writing the chapter, and without access to the book just now, I can't think of an example where a reduction in spell parameters might be useful.
Mark
Thanks for the reply Mr. Shirley.
My specific example was using Sjonhverfing at Personal (or Touch) range to affect a magical disguise (Individual) though truthfully I'm not really sure that's would be a valid use of that particular ability anyway since it seems more geared to Creo Imaginem effects as opposed to Muto Imaginem. In any case, I agree that in most cases there are indeed no benefits to be had by reducing the parameters (except perhaps for Hex which was already nicely addressed in the section detailing that ability).
PS. Sorry to hear about your ferret buddies. 
As you say, the illusion would be a Creo Imaginem, and 'cover' the real species rather than change the expression on them; I'd keep things at R: Touch. The magical disguise was one of the main uses in the Norse sagas; for example, a man trying to avoid a band of killers in Njal's saga (I think) was disguised by Sjonhverfing by his mother. When they burst into the room, all they saw was an old woman combing the hair of her goat.
Thanks. They were both very old, and had a good life; getting sick only right at the end. I'm now re-ferreted with a brace of young hobs who are spreading chaos back in my life!
Mark