system
Given the following post, respond as if you're commenting on Reddit:
human
[Fantastic 4] How thin can Mr. Fantastic become?

Also, secondary question, how far can he stretch/how much space can he take up?
gpt
He can stretch to about 1,500 feet before it becomes painful for him, flatten himself to the thickness of a sheet of paper, or make himself thin enough to pass through the eye of a needle.

I couldn't say how voluminous he can make himself.