I planed to make a belt with 1 con 1 uni save, +2 skill1,+2 skill2,+2 skill3,+2 skill4, with tire 3 from craftmastery.
If I start with +2 skill1,+2 skill2,+2 skill3,+2 skill4, then 1 uni save. I can add 1 con on top because the success possibility is not 0, and god save could help me.
But when I made a belt with 1 con 1 uni save, +2 skill1,+2 skill2,+2 skill3, and trys to add +2 skill4, the success possibility is 0 and I would lose xp on failure.
The later situation should not happen since they will end up with same products, and I would merely lose more gold on the later streagy.
However, this inconsistance result of Dweomercrafting has already ruined a belt of my character as well as a ring from loot.
Looking forward to the new Dweomercrafting system 
