You're confusing me, mate.
You've not ran him on fur, just feather,he has great prey drive, but you don't think he's running fast enough?!
Not following you at all!!
He 'might' be carrying a slight injury, which prevents him going 100% flat out.
Not saying he is, but it is a possibility.
Might be worthwhile getting him checked out.
Good luck with him, anyway. ?