use some tags like: futanari on femboy, stomach bulge, size difference - extreme size difference, futanari with a gigantic penis, femboy with a small flaccid penis, penis size difference, futanari is bigger, stretched anus.

apparently if you mix it with snickerz's v2 lora it does amazing work so try it out https://civarchive.com/models/550128?modelVersionId=655924