[ashleymoran]

Thanks for the replies both. Yes, this is one of the issues I have found: honesty over the risk in a project can make you look more expensive if you don't explain it carefully. This is especially true in a young relationship, when the client has not yet build up trust in the supplier.

Fortunately, I have found once clients are used to regular progress, they're more accepting of variation, and willing to accept estimates based on real statistics.