First I think I would go back to the engineer and have a chat, maybe a more standard size would work. It seems a bit strange that the spec would be an odd size.
The odds of a hole being drilled exactly to the bit size is small at best, drilling is a roughing operation. Due to the nature of carbon fiber, I would expect the hole to drill a bit smaller than the bit due to spring back.
That being said, I would try a #18 or a 11/64 drill bit. Both are pretty close. Then there is the problem of actually measuring the hole once it's drilled. Do you have a Go/NoGo gauge set or pin gauges to measure the hole?
I think some experimenting is in order.
I don't think you have a chance of trying to grind the drill bit.