Interested in the answer. As I have said, it doesn't actually matter how you do it as long as both pilots are in the loop and recommended manoeuvre/limit speed are observed.
It took me 5 seconds the first time I had a call (from a 'newbie' just out of line training) for F30 from F15 to realise that something new was being taught, to check the call and decide it was safe and subsequently to clarify both with the P2 and a TC it was 'SOP'. If you want to use F2, brief it, and if you have no PFD, use F1 manoeuvre speeds (also briefed!).
Many years back a Captain, downwind at FNC, called for F40 from clean/210. It worked - but it should have been pre-briefed..