SR Smith will give you the minimum depth but adding depth can make it a little safer up to a point. However, a deeper pool will have sharper slopes which can be an issue for some cleaners so that needs to be taken into account.
Our water depth is 9' but the board is pretty low and doesn't have much spring. We never had an issue with bottom scraping even with my daughter, who was on the HS diving team long ago, doing vertical dives although she would occasionally touch the bottom gently.
Also, you might want to check with your insurance company. Some policies have liability exclusion clauses for pools and/or diving boards. Also, some companies are now using Google earth to determine if a house has a pool or a pool with a diving board. I heard rumors of some who have lost coverage because of this. Luckily, I have not had that problem.