My bottles are usually marked as, for instance 10 ml, but hold closer to 11 or 12 depending on how full you get them. Not a HUGE variation in your flavor percentages, and the ratios would stay the same relative to one another but it might make things tough for new mixers. That said, I've done the same thing plenty of times.
To the OP, get a couple extra 1 ml syringes to save yourself time rinsing them out while you mix, and at least double the number of small (~5 or 10 ml) bottles you think you need. You'll want to be able to test the same recipe with a few different ratios and have them all steeping at the same time/ready to try.