I was struggling for a bit with how it applies to reducing damage, but got that figured out.
Since they're both Incidentals, how many have you allowed in a turn? Technically an Incidental is free, but should there be a limit? In the movies and shows they typically use these multiple times in a round. If it became an issue maybe I'd say 3 times? But maybe it's best to say, use it as often as you care to pay for, as long as you're not using it more than once on one specific hit.
How have you done it?