Back when I was hooked on those little blue pills the most I could fit into a 100unit shot was four but I felt like I was loosing some product still. I'd suggest at maximum doing 3 pills (90mg) per 100unit syringe. For six I would get two syringes and prep them both ahead of time, that way you get the full bang after the first one, just pop the second one right in. Watch out though this kind of use will lead you nowhere but trouble whether it be OD or awful WDs because you can no longer afford the habit at least that was my case and everyone else I knew.