By being endorsed on the single do you mean have a single Commercial license.. It sounds that since i have only a multi engine commercial i have to do all my hours on a multi which is going to be expensive.
Can I do this, do the checks on a multi the day, night and IR, and fly to rest on a single engine. Doesnt the PPL make my single engive hours PIC, so I can get a total of 15 hrs PIC.