You will most probably get a better time at selection, well nearly everyone did when i was there. It was all down to everyone giving each other encouragement, say if someone started to slow down somebody else would tell them to keep it up. One lad said to me, "just think, if you just keep going then your one step closer to a place in the army!"...it seemed to work and i beat my old time by 40 secs!
Just remember, its best effort.
zega