Mastic sure does brings a very peculiar taste (roughly speaking, think "Pine tree"!) to the ice cream, However, the proportions above should ensure a subtly flavoured ice cream, likely to be agreeable to most people.
Do be cautious if you want to have a stronger mastic flavour - in terms of strength, even a little of the "Tears of Chios" go a long way! Stick to the indicated amount, at least until you know for sure that you will like it!