Not able to switch mounted weapon arms

[(XBOX)Spiderwick3666]

I bought sevagoth deluxe and his side arm goes to his ghost arm instead of his metalic side and it looks strange, Id like to swap the arms of where the weapon shows up. And I know it's possible because it swaps when you have a glaive equipped and I'd like the option to not use the glaive when I want my side arm on the right side