Coring through Ohia Logs

[EightFingers]

I'd do this on a lathe. Drilling into endgrain is the pits! Mount your forstner in the tailstock (using a "jacobs" type chuck) and extensions as needed. Attach the other end of the log to a faceplate and mount on the headstock. Those extension would need to be pretty robust to keep them from wandering off-center, tho'. I've used this method successfully to about 24" with 2" diameter forstner bits.
This might be a good question to pose to the Hawaii woodworkers' guild or even the woodturners' club.