This is an adapter to use hein0170's backseat cinema iPad mount on a car with a less exposed headrest bar. It is done in openscad so modification to other headrests should be relatively straightforward. I was inspired by RyGuy's headrest mount system giving this design a simpler (although less sturdy) mounting mechanism than hein0170's.
Be sure to read the instructions before printing.
You will need to print out the iPad holder portion from hein0170's backseat cinema and assemble it as he indicates. You will need two rods to span the distance between the headrests poles. Since they were easily available at our hardware store, I made the mount file to fit 3/8 in aluminum rod. You'll have to drill the holes out slightly if you go with hein0170's 10 mm rods. The only other hardware needed is for hein0170's iPad mount...
5 pcs M4 30mm (or preferred 25mm) bolts
5 pcs M4 nuts
one rubber band (optional)
Adjust the "hole" openscad file if you need a different diameter head rest hole or a different depth to the iPad mount. This holder is going to take a lot of abuse so print it out with as much fill as you can, 80-100% would be best. You can generally fit several parts on the same plate. You won't need support,
Once printed, you'll probably find you need to hammer the rods into the holes on the mount. It is suppose to be a tight fit. Be sure to put on the iPad holder before you put on the second end piece since it is difficult to get the rods out of the end mounts. You can add a rubber band to hein01790's design to make the top clamp spring loaded (see the 3rd picture). This is particularly handy in this situation (where the headrest is in the way) since it is a pain to tighten/loosen the screw every time you want to secure the iPad.
To install it in your car, hook the hole pieces around your headrest holes and then slide the hooked ends into the mount pieces to secure the iPad mount. It should all be a tight fit. My print has plenty of friction to hold it all together. You could always glue the parts or add a screw if you wanted a more sturdy fit.
The mount is less sturdy than hein0170's, but it is my only choice with my current headrests. So far I've used mine for almost 9 months with no obvious wear and tear (short of replacing the rubber band).
Update: The optional rods file can be used to print 160mm long rods instead of buying the aluminum rod, if this size will work for you. It was reported by ConstantineC that ABS is plenty strong when printed with 100% infill. I've not used these ABS rods so let me know if they need any adjustment.