I have 2 mungo pines on top of a mound near my pond in the backyard. They were there when we bought the house 9 yrs ago. They are a beautiful addition to my landscaping and waterfall, however, I was thinking of trimming them down a little as they are looking large, bur I have never trimmed them and am afraid that they will go in shock and die or trimming will make them look awkward. How much and when do I. Thank you