I am not sure how more power from a big kite would "pull me downwind", but not pull a bigger guy downwind. Doesn't seem logical. True power should not pull anyone downwind. It's not like my legs aren't as strong or stronger than just about anyone's out there.
In terms of size/weight, leg strength determines how much kite you can hold down, not how much you weigh. So, no kite is going to pull me downwind (not in sub 15), unless it just sucks.
Also, a larger board should "make you weigh less" by displacement. So, a big guy on a bigger board should theoretically "weigh" the same as me on a smaller one. I use a 130 by 40 once it hits 11/12 knots.

Anyway, my take is still that big kites "feel powerful", but much of that feel is just the feel of drag.

I have been talking about wearing a 50 pound weight belt and riding for years now just out of curiosity. I am gonna give it shot this year.
Maybe those big a.ss kites are useful for big guys and I am just clueless. Still seems like a larger board would negate the need for a monster kite though.

I mean, I can ride a 9m in 9 knots (upwind with eyes closed) on a Glide. So why can't a guy bigger than me apply the same principle?
My reasoning makes sense to me, but I am gonna wear the weight belt out next time to test the theory (nothing better to do in ten knots).
Sometimes reality defies logic. Anyway, just throwing theory/opinion around..... waiting on wind.