there is no set rule,,
ask what will make the project worth it too you,,
just because you ask a price does not mean the client will agree,,
so ask what is good for you and you feel good about,, and be flexible if want to,,,
its seems you are saying the bow will be more challenging than what you usually do,
if it was me I would ask double my normal price,, and go from there depending on how the clinet responds,,