englishal
Why do you think you have to be "sole manipulator of the controls" to be the pilot-in-command of a SPA? You're going to have to quote a reference (from the devil) for me to go along with that one.
I would think virtually every PPL holder, has taken up friends and family, then given them a go at the controls. Nothing wrong with that, not illegal, don't need to be an instructor, if it's not used towards the requirements for a licence or rating.
Every flight I do as a FI, I'm PIC of a SPA, but never "sole manipulator of the controls".