Agree with Garvin re: honesty and competency. If you had sold your soul you would have been the SOB they would have abused when things didn't go right with the cowboys "you" recommended - those consultants would have hung you out to dry also.

At the end of the day it comes down to integrity for me. I had a similar dilemma related to a delivery date for a s/w app which as PM I had created the schedule for so I quickly found out we had a snow balls chance in hell of achieving the date my bosses wanted. Although a contractor to the organisation in the end I wasn't prepared to lie to a client about something that I knew was fundamentally not achievable. Found myself out of contract soon after but upon making that call and leaving you can't imagine the relief. I slept better for making that call and the work still rolls in.