I have some open bars/on mary/low sweep/curve back bars on my Trek Transport. They came with Ergon integrated grips/bar ends and I really like them for the cargo bike. I also have Jones Loops on my Pugsley and while nice(and I thought I might put them on the cargo), it turns out I like the angle better on the open bars for hauling. I had MTN Drops on my pugs for a while(Woodchippers) and drops are nice for hand positions BUT sortof put you more aero and over your front wheel, which for hauling, would be odd. Haulers usually ride more upright like a hybrid, so more hybrid type bars or maybe even MTN drop type bars(meant for more upright seating than say, typical road curl drops) might be okay. Not great, but okay.