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"what fields should I set on Wahoo to be able to 'ride within myself' and then attack the person I am riding with on Corkscrew hill?"
Exactly what I said then. 3 or 10s power to keep any spikes low. The ride out is of no concern - you either keep up with the person you are competing with or you don't so FTP is irrelevant and the climb, as I said just above, is also too short for FTP to have any bearing on results.
Are the two people not riding out together? If it's a long, self-paced ride out then FTP may have an impact but then you would be riding WAAAY below threshold to save energy for the explosive climb so oh look FTP irrelevant again. Unless @amey is the pace-setter for the ride out, which we don't know, FTP% is irrelevant.
How long is this climb? Why would you be staying under your FTP for something that lasts a fraction of an hour? This is a London climb right? You should be riding it at 2xFTP maybe with bits at 3xFTP