Gents, thank you all for your replies. Well done to hetfield who correctly spelt out my error - should have been "parking brake set" in the original posting.
Buzz Box, I would be interested if you could point me in the direction of any further info re. Boeing's tests on the main gear steering unlocked scenario.
As a progression to this, would you choose to reject for the parking brake set master warning at let's say, five to ten knots below V1, assuming no other abnormal indications?