Add warning about using the right versions of STL files.

Author: gluap

README.md

@@ -63,6 +63,11 @@ is meant to get you started, without having to check for compatibility and
 without cross referencing multiple parts of the documentation to build your own
 version of the device.
 
+
+
+> **Warning**
+> We only keep the rail shapes constant between versions. When printing make sure that your ``MainCase`` and ``MainCaseLid`` come from the same release. The same is true for ``DisplayCase`` Top and Bottom. The Idea is that OpenBikeSensors can be mounted on a different bike with older version mounts, but the current version lid won't necessarily fit onto last years case.
+
 To get a standard variant, print these parts:
 
 ```

export/README.md

@@ -1,3 +1,6 @@
 # For the most recent release you can find the files conveniently zipped [here under "assets"](https://github.com/openbikesensor/OpenBikeSensor3dPrintableCase/releases)
 
-This folder contains the stl files for convenience. It is recommended however to download the latest released files as a zipped bundle [here under "assets"](https://github.com/openbikesensor/OpenBikeSensor3dPrintableCase/releases) instead.
+This folder contains the stl files for convenience. It is recommended however to download the latest released files as a zipped bundle [here under "assets"](https://github.com/openbikesensor/OpenBikeSensor3dPrintableCase/releases) instead.
+
+> **Warning**
+> We only keep the rail shapes constant between versions. When printing make sure that your MainCase and Lid as well as DisplayCase Top and Bottom come from the same case version. The Idea is that OpenBikeSensors can be mounted on a different bike with older mounts, but the current version lid won't necessarily fit onto last years case.