I took before and after pics of my V20 with the stock M chain stay and then with the L replacement:
As you can see the crank shaft was about level with the seat bottom with the M chain stay above, and it is now just above the middle of the seat back. This made the boom slope shallower, and now my sight line is right down the top of the boom like the barrel of a rifle. Before I was looking at the bottom of the boom.
One thing I noticed on my test ride is that the higher crank position closed my hip angle slightly, and this seemed to make it easier to climb on shallow slopes. This is just my first impression, so it may just be an illusion.