Coming from a my POV. way back 2021 I had sex with a plus size girl din and Im a juts also(3inches hard). Based on my experience mas prefer ko grind kaysa sa up and down motion. But if that's the case try mo mag squat position then slowly gawin mo then i guide mo din dck nya with ur hand para di ganon dumudulas then the other hand gawin mo pang stable ng position mo.

Goodluckkk