Another consideration aside from safety is to check your local bicycle laws. Here in Washington, it's illegal to boost somebody for a ride on the rack/bars/pegs, etc.
RCW 46.61.760 Riding on bicycles.
(1) A person propelling a bicycle shall not ride other than upon or astride a permanent and regular seat attached thereto. (2) No bicycle shall be used to carry more persons at one time than the number for which it is designed and equipped.
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"I feel like my world was classier before I found cyclocross."
- Mandi M.