Hi mate, it's really easy to reduce power to less than 12ftlbs, BUT even if you do that the rifle will remain an FAC registered rifle. Once an FAC, always an FAC. There's no way around it I'm afraid.
No, wrong, false, tripe, balderdash, hogwash, falsehood and lies.
It depends on the police force where you live. Norfolk will allow FAC guns to be taken off register as long as the work is done and certificated by a registered firearms dealer.