Well ...
The two aircraft shown in post #49 have the same L/D at about 226 kts. At that speed, and only at that speed, both airplanes slow down at the same rate. As the speed reduces below 226 kts the L/D's of the two aircraft will change differently and hence the rate of slowing down will be different, as shown in the graph.
P.S. I deleted the above immediately after posting it Because I saw that while writing there had been several new posts and I wanted to read those first. Sorry for any confusion.
P.S.2 I suggest you could consider the component of weight that acts in the direction of the flight path as the glider's equivalent of thrust, but momentum is not thrust.