What do you mean by "do not modify abilities permboost?" Do you mean those +con +speed +sneek stuff? Can we modify resistances or HP boost?
Every generated item has an existing PermBoost called "Abilities" that is exposed by the editor. It is there by default whether or not the item has any permanent boosts on it. I am not sure what it does yet and modifying it may cause problems. You can still add/remove stats; this has no bearing on modifications to the item itself. I may just hide this "Abilities" attribute until I can figure out what its purpose is.