First race of the year, coming right up on Feb 24th.
It's a shortie - 9 mile (14.5 km) flat TT - so really it might be too short to really see much of a quantitative difference from the helmet... I did do the same course last year (hopefully I have the results somewhere so I can compare this year to last)

I don't really train on the disc - its a tubular, so its a real PITA to change the tires... I'd hate to be training on it and get a flat, so if I train on the TT bike I do it with regular wheels. The disc is a bit heavy, but I think on a flatish course its well worth it. Rolling is OK, but for very hilly I'd leave it off. I use my road bike for hillclimb TT's - its just lighter all around and you don't get going fast enough to take advantage of aerogear anyway on a hillclimb.

I'm going to talk you into a skinsuit someday I don't know how much of a difference it really makes, but d*mn it feels good (fast) to wear one...