I have also posted two photos of actual snake rail fences that can be found at Gettysburg today . . . . as you can see, the H&A snake rail fence looks very much like the "real deal" . . . .
Mike,
Just a few thoughts here; First, your diorama looks great. While I know that Mr. Osen is dedicated to historical accuracy in all his products, I have wondered what particular example he used to model this fence. I'm no expert on 19th Century agriculture or architecture, but I have seen a lot of rebuilt CW era fences at NPS sites/historic farms over the years and looked at the period photos, drawings, descriptions, HABS, etc . I have never seen a CW era snake-rail fence built with a rock wall piled underneath. This would be an unnecessary amount of hard labor to build it this way.
The fences being repaired in the photos are not snake-rail fences but are called "stone and rider" fences. George R. Stewart described these fences on Cemetery Ridge in his book Pickett's Charge: " the walls, here, were low - two feet; three, at the most. In fact, many of them would not restrain a cow, and so they had been heightened by having a rail fence stradddled over them, the result was very practical - the wall pig tight, the fence, cow high."
The rock fences at Gettysburg are generally built on a straight line at the field boundary - it doesn't "snake." There is no need to angle them every 11-12 feet for the supports and the two rails, or "riders". The supports and riders follow the straight line of the rock wall and the two rails are high enough to do the job...which is the way they are usually recreated at Gettysburg today.
The snake-rail fence was common in 19th Century America, especially where the farmland did not provide an abundance of rocks to build walls. The usual snake-rail fence is angled, (or zig-zag) in order to stack the rails. Once the rails are cut/split, it is relatively easy to build the fence. There is usually a flat rock at each angle keeping the bottom rail off the ground. The "x" support and rider both anchor the fence rails and add height.
I'm sure Mr. Osen has based this fence on a period example, but it would seem to be an uncommon type.
Oddball