I have a Brompton customised by Kinetics and a chubby trailer. If I fold the bike and lay it on its side, the parts on top are only supported in two places:

• at one end, by the frame-hinge
• in the middle (near the fork hook), by the front hydraulic disc brake caliper pressing against the chainring guard

The chubby doesn't provide any support/protection against stuff being placed on top of the bag when the brompton is inside.

How is the middle supported in a normal Brompton? How much weight can it support?