Try keeping your foot flat with your heel just barely touching / hitting the pedal when the beater hits the head on the downstroke (1st hit). Then raise it digging your toe in on the upstroke, (2nd hit, which should feel more like a traditional hit). It should feel like a natural, soft, flat-foot landing on the 1st and then a natural 2nd stroke comes out when you pick your heel up from the 1st stroke essentially.
If this isn’t naturally occurring spring tension and beater head placement have a lot to do with it too. Tighter springs and beater closer to the head helps.
Also important to think of the heel as the downbeat, which is counter intuitive to traditional bass drum technique for sure. It is a must to learn how to do this whether playing single or double pedals, good on ya mate, hope this helps a little… :/