Can I log PIC time while flying solo in an R22 toward a helicopter addon? I hold a PPL/SEL and I'm training for a helicopter addon. I'm training in a Robison R22 which is subject to SFAR 73. Can I log my solo training hours as PIC time? FOr student pilots, with solo endorsement, I believe the answer is yes.

However, SFAR 73 2.b.1.ii says, "no person may act as PIC of an R22 unless that person ii) Has had at least 10 hours of dual instruction and has received an endorsement from a CFI..."

Is this a different endorsement from the solo endorsement, which I obviously have to fly my solo flights? 

The reason I ask - I want to know if my time flying solo counts as PIC time toward my commercial requirements.
Solo time is always PIC time. You're alone in the aircraft, so who else could be PIC?

14 CFR 61.51(e)(ii):


  (e) Logging pilot-in-command flight time. (1) A sport, recreational,
  private, commercial, or airline transport pilot may log pilot in
  command flight time for flights-
  
  [...]
  
  (ii) When the pilot is the sole occupant in the aircraft;