Re-read what mathloser actually says. He plans to keep on gaining weight by eating in a surplus, just not gaining strength or (therefore) muscle. No he will not look like a 150 lb skinny but ripped guy, and yes he will fill out an XXL t shirt, as well as a 50 inch pair of trousers. Might need to resort to a pauncho
Mathgainer, I'm not sure how old you are. As a 59 year, I can assure you that unless you're aggressively trying to gain strength, you'll lose it. I'm not sure why exactly, but from my experience, if you go into the gym trying to maintain a certain level (i.e. 300lb squat), it will just get harder and harder resulting in a decline in strength much faster than if you were pushing yourself as hard as possible in an attempt to gain strength.