My highest (with proof) is 298. Like you, I'm sure I tipped over that by about 10-15 pounds at some point, but never weighed myself.

The lowest as an adult, I don't know. I know I was in size 20-22 jeans after high school, but I'm not sure. I would guess around 220/230.

I can't wait to be less than 200 - It's been so long.