Welcome Jrsower!
IMO you are a little low. I like to be in the 18 to 23 feet range. Just high enough so that I'm in the under canpoy but not so far up that if fources unnecessary steep angle shots. If I were you I'd go a bit higher but I've also shot seer at the heights you've mentioned 12-15 feet.
IMO you have to way the advantages of both being high and being low. Shooting is easier from a lower altitude but getting busted is easier. the higher you go these two flip flop to a point where shooting is difficult and get busted is unlikely. The happy medium that I've found is in the 18-23 foot range. Some trees will take more some less but in this area is where you'll fine me in a tree.
