If you watch Henrick Mortensen's video you'll see how he turns his upper torso to reach back into the D loop and to begin the forward stroke. I've tried this and found that (especially) with short bellies it creats a lot more line speed without more effort and effectively lengthens the stroke. Best way to visualize this if you have not seen the video is by imagining you're standing fairly square to your target and you perform your standard cast, but when you get to the point where you've set up your D loop and you are raising your right arm at the pause/drift (assuming you are right handed) turn your torso so your upper body is facing almost upstream. This moves the right shoulder farther back, and when you begin the forward stroke the first thing to move is the right shoulder coming back forward by turning to face back towards the target, followed by the cast as you would normally have done it.
If you're unsure of this, grab the butt section of a rod and pantomime a cast. Stop at the end of your D loop stroke and see how far back the rod is from your feet. Now do it with the upper body twisting away from the target towards the D loop and see how far the rod is from your feet now.
I was amazed at how this not only lengthens the stroke but creates a higher line speed with no more effort.
If you're unsure of this, grab the butt section of a rod and pantomime a cast. Stop at the end of your D loop stroke and see how far back the rod is from your feet. Now do it with the upper body twisting away from the target towards the D loop and see how far the rod is from your feet now.
I was amazed at how this not only lengthens the stroke but creates a higher line speed with no more effort.