Check-in usually opens around 1200 Friday, the sooner you check in the better. Due to the larger amount of players lines form really quick - so in order to save you time for other things to do throughout Friday, check in as soon as you can (it'll save a lot of headache in the long run, trust me). As for your question on Chrono As DEB already said, AMS uses a non tamper seal to mark that you've been chrono'd. If you change springs it will "void" that chrono and you'll have to do it again. That chrono sticker is good FOR ALL WEEKEND. You DO NOT have to chrono daily unless you "void" the sticker (can only be done be either removing it or separating the two receivers to access the gearbox).