All spirits have attributes expressed in terms of F+M, where M is some integer value, positive, negative, or zero. As their Force changes, higher or lower, so changes all their attributes. This is universal, except... when we deal with a special case, like allies.

Ally spirits have only physical attributes expressed in terms of F+M. Their mental attributes are static(those of the summoner when they were created). We could create another thread to discuss it, but I'm under the impression the value of M can be changed by the summoner, rather than the attribute directly, during Ritual of Change uses to increase an Ally Spirit's physical attributes(i.e. a Force 3 Ally Spirit, whose Body has been increased to 5, would have a Body of 6 if its Force were increased to 4).

If this is true, though, it makes buying attribute points en masse at lower Force a good idea.

If it's not true, because Force doesn't increase their physical attributes, it either makes Force much less useful to an ally(and makes them unable to advance in all but Force, at all, if they become Free Spirits, since there's no other listed way to improve their attributes). An example of this would be the aforementioned Ally having Body 5, Quickness 3, and Strength 3, even at Force 4.

If it's not true, because Force doesn't consider modifications to attributes, it makes Ritual of Change(Increase Physical Attribute) less useful, as changes made in this way would be eroded as Force increased. An example of this would be the aforementioned Ally having Body 5, Quickness 4, and Strength 4, at Force 4(thus eroding 1 point of that improved Body the caster paid good dishonestly earned karma for).