I've noticed that several of the aftermarket rear racks for Brompton look generally smaller and less substantive than the stock rack -- e.g. on eBay, one can find the "Q type" rack and the "Ti Parts Ultralight" rack. That sounds well-and-good for reducing weight/space...

But I'm a little confused about functionality - what can you carry on such a small rack? With a larger rack, it seems plausible to use bungees / straps / zip-ties to attach (say) a dry-bag, a small duffel, or a milk crate. What fits on a tiny rack?