About the rear rack:
- On the Brompton, the rear rack use is very limited because anything wider than the rack will be hit with the heels while pedaling, so its not compatible with rear pannier. The rear rack slightly increases the folded height. But the front block is a great solution to carry things, it allow to carry a 30l/10kg max bag without influence on the steering.
- On the Helix we don't know yet. There are video showing Helix with two very different rear rack, we don't know what will the commercialized rear rack be, we don't know if it must be removed to fold the bike, we don't know if it will increase the folded size?
- On the Birdy: its the best available rear rack on a folding bike because it is fully compatible with full size rear pannier (for instance from Vaude and Ortlieb) without risk to hit them with the heels while pedaling and the rear rack automatically folds when folding the rear swing arm without increasing the folded size and its specified for 20kg.