100/150 hours aside....
I would say you could use you P.1/s time - I certainly did include it in the P.1 column when applying for my ATPL.
Example of why - Say on your PPL GFT, you pass. You get to mark that time as P.1/s, but if you fail the time goes down as Pu/t. In the first case you have demonstrated the ability to be the commander and in the second you have not.