Personally, I wouldn't (and don't) go getto tubless without these:
FattyStripper Tubeless Fat Bike Solution and SkinnyStripper Tubeless CX & DH Solution <link rel="image_src" href="http://fattystripper.com/media/FattyStripper_Logo_320.jpg" / ><link rel="image_src" href="http://fattystripper.com/media/FattyStripper_L
Its going to prevent your tire from burping (and make easy to seat, and make sure you don't have any rim leaks). Very very inexpensive insurance.
Not your first race ever, if you have already done 3?
FYI, I'd do the back tire if only doing one. 90% of my flats are on the back tire, and if it burps I can go down gracefully. A sudden front tire flat is gonna cause me to hit the deck.