S turns
The answer will to some extent depend upon whose aeroplane you are flying. If it belongs to a school, club or syndicate, they will no doubt have an order book that specifies the precise requirement.
If its your own, then you as the captain will be required to make an executive decision, as compliance with the Rules of the Air and avoiding a prosecution for endangerment, are your responsibility.
In simple, don't use anyone who is not qualified to act as PIC in the prevailing conditions, after all, you did say "some of it will be in VFR conditions" so presumably, some of it is under IFR.