Yes...... Tapping the No1 threads to BA was authorised in the EMER's and a list of those it applied to was specified. I don't know whether it applied to the offset sling loops but given that equi-sided loops were available on the No1 rifle, then a No4 one would be readily acceptable....... unnoticeable even! We use the practicability route. And while I learned straight speaking in Australia, I learned the art of practicability in New Zealand