[MetroMPG]

Sure, but what do you do when the truck (if it's a truck) speeds up going down hills?

I didn't say so in my original post, but I adjust my speed to match the vehicle I'm reverse drafting, including trucks behind me on hills. Common courtesy.

I also speed up for trucks approaching from behind if I'm driving slower than average - solo - if they don't have an immediate opportunity to pass me. Once they're by, I drop down again.

And this strategy may not be practical using heavy trucks on hilly roads.