You need :
-Ficedula LGP tool
-Borde's Kimera 0.93 (the 0.95 dont work properly with field characters)
In your FFVII data folder you take in the char.lgp file in the field folder, then use the LGP tool to open this characters file and extract all in a new folder. Than you use the Kimera, open in the character folder you created, and searche for cloud with sword model : bhff.hrc
Then save the model in a new folder, Cloud sword folder. Use kimera again to find the base cloud model : aaaa.hrc, save it in another folder, Main cloud folder.
Open the models in two separate windows with kimera, then save the sword from the cloud model with sword, in a p file which you will name "sword" in the Main cloud folder, then in the Main cloud kimera's window, you click on the back from cloud model and in the bones options you add a new bone, the sword p file, then you adjust the sword to his back, you save the model and you copy/paste the Main cloud files in your Character folder. At last you create a new char.lgp file with ficedula lgp tool and you put this file in your FFVII data field.