450 sounds a wee bit high to me, it should be around the 300 mark
Try setting your rex about midway then set the input to about
300-350, see what fps you get, then just fine tune from there.
Ive had a nagging doubt that it should be nearer 300 than 400 but didnt want to play around too much at the tourney incase I missed a game, managed to chrony down to about 276fps by going large with the freak insert to allow more air around the ball.
Ill give it some time this weekend and sort it out.