Morithiel,
I've been fiddling with the equipment list for my character and his artificer cohort, and a couple of questions came up. Can I craft custom items so long as they unambiguously follow the item creation rules? Specifically, I was interested in a Use Magic Device skill enhancer combined with a Hat of Disguise (paying the bonus squared X 100 for the skill enhancer part and multplying the cost of the hat by 1.5 for multiple abilities). I was also interested in boots that provide a deflection bonus to AC (paying 1.5 times the cost of a similar Ring of Protection for the unusual slot, considered wonderous).