Adding Abilities

[Xedrek]

So I asked my GM if I could add Muleback Cord properties on top of my Cloak of Resistance (they take the same slot). He said I couldn't do that because one base item is a cloak and one base item is a cord and that it didn't matter that they took the same slot.

Adding Abilities:

Sometimes, lack of funds or time make it impossible for a magic item crafter to create the desired item from scratch. Fortunately, it is possible to enhance or build upon an existing magic item. Only time, gold, and the various prerequisites required of the new ability to be added to the magic item restrict the type of additional powers one can place.

The cost to add additional abilities to an item is the same as if the item was not magical, less the value of the original item. Thus, a +1 longsword can be made into a +2 vorpal longsword, with the cost to create it being equal to that of a +2 vorpal sword minus the cost of a +1 longsword.

If the item is one that occupies a specific place on a character's body, the cost of adding any additional ability to that item increases by 50%. For example, if a character adds the power to confer invisibility to her ring of protection 2, the cost of adding this ability is the same as for creating a ring of invisibility multiplied by 1.5.

I need some clarification for his sake that there is no rule pointing that out or clarification for my sake to say there is.

[Xedrek]

There is also this text in the CRB about swapping the base item.

example:

Some new items are really existing magic items with a different weapon or armor type, such as a dagger of venom that is a rapier instead of a dagger or a lion's shield that's a wooden shield instead of a metal shield. For these items, just replace the price of the non-magical masterwork item with the cost of the new type of item. For example, a rapier of venom has a price of 8,320 gp instead of the dagger of venom's price of 8,302 gp.

[Dave Justus]

GM of course has final say on any custom magic item. Reasons they could disallow it include flavor, so not wanting muleback cords to be able to also be a cloak is legitimate.

However, from a rules perspective, they are both just 'shoulders' slot items, and a cloak of resistance +1 with an additional magical property identical to that of the muleback cords for an additional 1500 gp is as valid as any other custom magic item.

[Lifat]

Dave Justus wrote:

GM of course has final say on any custom magic item. Reasons they could disallow it include flavor, so not wanting muleback cords to be able to also be a cloak is legitimate.

However, from a rules perspective, they are both just 'shoulders' slot items, and a cloak of resistance +1 with an additional magical property identical to that of the muleback cords for an additional 1500 gp is as valid as any other custom magic item.

+1! The GM is totally within his rights to reject it from a thematical viewpoint. He is also free to reject it because of power level or other such reasons.

The item is not against the rules however, so if that is his arguement, then he is misguided.
Personally speaking the only good reason I can come up with for refusing this particular item is style/theme.