the idea of the Reflex Tensioner is to put tension on the batten from the inside point of the sail and not from the end. So, release the tension at the batten at the normal batten tensioner in the end and tension through the Reflex Batten tensioner the batten afterwards. You start with the tensioner just next to the boomend and work youself up till the top. You can put most of the tension on the batten tensioner next to the boom and by each Reflex tensioner up a bit less tension. Afterwards you can tension the batten at the sailīs end. Minimize the tension on the top battens of your sail in general and give your sail the chance to breath and flex.
It does not matter too much if the wind is light or strong. In general you would change your boomend tension or take a smaller sailsize. The Reflex tensioner in general allows a better release of overpower due to the fact that the leech reacts and can flex (breath).
Sure you should use the recommended mast or anything similar in stiffness and also check the pressure of the cams, where you can adjust cam spacer or take them off.
Here is the link to the Severne website: http://www.severneracing.com/reflex_system.php
Hope this helps,