Are you sure about that last part? Obviously, if you are solo without a CFI on board, you can log it as PIC. But if you do not have a Private Helo Rating, I don't think you can log PIC time as "sole manipulator of the controls" while practicing the maneuvers for the Commercial Helo - and thereby building PIC time towards that rating - with your CFI on board. When I did my FW to RW 15 years ago, I got out my calculator and figured out that it was cheaper to pay the $200 for the Private Pilot checkride, so that I could log PIC time while working (with my CFI) on all my Commercial Helo maneuvers ........ vs. not being able to count that time with my CFI as PIC time (if I did not have a Private ticket) and then have to just go out and fly around (more) solo to build up my PIC time to the Commercial requirements. But I could be wrong.