Thanks Gomer. I did drill two holes (one spot on) and the one that is off is only slightly off. I can just see the side of the hole. Part of the problem was that the cylinder has been ported and the bridge is very narrow. The other part was that I tried a new method to keep the drill bit from moving on the piston. Basically, I put masking tape on the piston and marked the tape. I use this method when drilling into an a slick, irregular object that I cannot use a punch on (tile, glass, etc). It usually works well, however, in this case the bit did move slightly and I didn't notice it with the tape.
I will most likely see how it runs with it the way that it is. Definitely will be more careful next time.