Well it depends on how fat someone is to be blunt. ….
If you’ve got a 32-in waist the regular size is more than adequate
If you’ve got a 40 inch waist….probably not…..
I’ve opened my puffy up and laid it on top of my upper body under my 20 enigma quilt many times with no issue…… Now I leave my sides loose… I don’t use straps…. So I consider the quilt normally good to about freezing…. And into the upper twenties when I add my light puffy across my chest. And that’s after I added 1.5 oz to the original quilt……. It’s ratings were a bit optimistic
I have tons of room in the body….. The real issue is towards the shoulders where it gets a bit tight when it snapped around your neck, that compresses the insulation there and makes it kind of a cold spot
If it’s under 25 I’ll bring it 10° quilt