I have to admit that over the years I've shown up at the NW Regionals many times with an unflown plane. Sometimes it came out OK, but usually the normal teething problems a new plane has kept me from really doing well with it. More recently, if I have a plane that is largely not been flown, I take a well flown and known backup. That's the plane that usually gets the time when in comes down to it.
This year I will bring a new plane, but it has 15 or 20 flights on it and the gross trim is done. While I don't expect to surprise anyone and certainly don't expect to place very high, it should be a competent flier.