Nothing else may be carried. The limit is there to keep you on the right side of airline and customs rules.
For carriers
You are flying anyway
An envelope weighs nothing and takes no space. Post the route you already booked and let it cover your transfers.
Join the listHow carrying works
Being chosen does not tie you up. Until the sender pays you stay visible on other requests and can withdraw.
The reward is already held before you collect. It reaches you once both sides confirm — or when the confirmation window closes.
Before you take a job
Open every envelope handed to you and check what is inside. You are the person carrying it across a border, and no platform rule changes that responsibility.
Anything that is not a document or a key, refuse. Anything you are unsure about, refuse. Support will back a refusal every time.