Advantages of thinner, ligher arrows for 18m recurve target shooting.

BrokenArrows

Im currently shooting Easton XX75 Platinum Plus Arrow 2016's.

Im getting to the point where my groupings are pretty tight and im thinking about what else i can do to bring it even closer.

Basic theory is a heavier arrow will travel slower than a lighter arrow shot from the same bow. Since its traveling slower it has more time to drop due to gravity.

So in theory a light arrow will have a straighter trajectory than a heavier arrow.

But the questions is, how much of a difference does this really make at 18m?

My arrows come in the range of 1416 up to 2315. What sort of drop difference is expected from both arrows?

Edit: As a side question, does any arrow/poundage combination achieve a perfectly straight flight path from bow to gold at 18 meters?