+1 to everything SheFly said - great advice.
A lot of the 4's here show up with road bikes and many have no aero equipment at all, so that is not a worry. Definitely do a recon on the course, and bring a trainer to warm up real well before your race.
One more note, ask whether iab is allowed at that specific race, if the TT course is not too technical that will save you a few seconds here and there compared to just being in the drops, because it's a tad bit narrower.
I hope you are still planning to race your TT in April, and please do post a race report