I just finished my PMEL, and it was 15 hours in the plane. However, that was at ERAU, so I am sure it can be done with many less hours. I personally felt extremely comfortable in the aircraft after that time, so I say take it at a pace that gives you not only comfort but also confidence for your checkride and subsequent flights.
Most places I have tried to rent a multi at after my checkride want 10 hours in type, and 15 hours PIC. Stupid insurance, but I also understand that due to a pockmarked history with twins and low time pilots.