BFTS - 20 started, 3 scrubbed and 7 back-coursed for various reasons ie med, weather delays etc. The 3 scrubbed were all good blokes where personality/attitude would not have been an issue.
As I understand it, from the student point of view, you have to have the ability (hands and feet, push and pull) but what makes you passable to the next stage is your spare capacity to deal with other than ops normal stuff. The QFI's are not unrealistic at all with their expectations, they too 'have a bad day' every now and again.