John,
We're specifically counseled to advise ATC on our actions, as they won't know what we're doing, and won't have access to our turn procedure.
When I stated that the climb gradient isn't the issue, my meaning was that we may or may not be able to meet the departure procedure climb gradient...but that's not the reason we're using the turn procedure.
If there's a special turn procedure published for that runway, we're going to use it, regardless of whether our climb performance would enable us to meet the clearance departure procedure, or not.