Easy enough to make, I made one for a mini, but the main problem is finding what the mounting points on the shell are then just making stands to bolt to these. Just make the stands as wide as you can to give as much stability as my first attempt with a mini almost ended in disaster as one stand fell over as car rotated, fortunately mini not to heavy so held onto it till my dad could get a jack under the car. We then made then so they where slightly wider than the car and had no problems since.
Hope this helps