As MixMX23 is my brother, I know his swing pretty well. Jeff is more of a swinger (start-up swivel) and likes to feel the pull down with CF. However, having some softball swing still in his game, he also likes to apply some right arm thrust (with a bit of the right shoulder coming around vs. down). I agree with the above answers, but also offered this to him:
Take a club in each hand and go to to impact fix. From there, keep the left hand/club in place, while swingwing the club in the right hand to the top. Once at the top, look, Look, LOOK to see what he needs to do to get the right arm and club in hand to meet the club left at address. As I also was a bit of an over the topper, it was eye opening to truly feel what the downswing should feel like when the right forearm comes down on plane (vs. too high).
FL-John
P.S. Don't listen to Dad!
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"If you can't yet do it on the angled plane, go back to the horizontal plane until you get it right"