Well,, I don't think he'll be sipping 200w. But he can carry 16 ah,, but carry only 8 of in in his relatively small triangle.
Custom is the key,, if a small frame mount pack fits, it can start with that. Then parallel something else, like a less than 10 pound rack pack.
It just depends on his needs. For my hauling ass off road, I carry 10 ah, 8 ah usable of lipo. I pull 2000w all I want, but by the time I use that pack up, I'm used up riding that hard. about 8 miles of riding is plenty at that power level.