Well, I called the Hawai'i Dept. of Health. The woman I was talking to said that the 'certified letter' definitely is a letter stating that there is 'NO RECORD' in the Ka'u District for that date - 26 February 1888/1894, for Grandpop Dave.
So where to now?
Maybe I should write to the various Historical Societies in the Islands?
Maybe try the Sugar Plantations?
I think before I do that I need to go over the information I do have very carefully and see if I missed some other clue. There has to be some way of proving that he was born in Hawai'i.