In the lower Cats, typically, as long as it's not a National Champ event, the race officials don't care what you ride. Last year at the State TT I saw a guy racing a Trimble frame. I've also seen Softrides, old Zipp frames, etc. What Cat are you entering? As for getting comfy in a week....it depends. Depends on your fit, frame size choice, back, hamstrings, bar height, seat choice, etc. etc etc.