Rate coefficients of a class of prototypical insertion reactions, namely X + H-2 -> XH + H, where X = C(D-1), N (D-1), O(D-1) or S(D-1), are systematically investigated with ring polymer molecular dynamics (RPMD). Besides giving accurate rate coefficients by correctly including quantum and recrossing effects as in previous work, we have tested the effect on the results of the choice of the dividing surfaces. Our results explicitly confirm a key property of the RPMD rate theory that the choice of the dividing surface along the reaction path has no impact on the results.