Best thing to do mate is go for a full weld in cage, either custom cages or Fabricage will supply and fit if required. A cage is not just for show, if you have one it might as well do the job that it is intended for. Also go for the door bars they stiffen up the shell no end and if your serious about it have the cage triangulated to the strut tops.
Have the shell seam welded and use the car for what it was designed for rallying.
Failing that come and have a play in our cars on gravel, cheaper than you would think and possibly the best thing you can do with your clothes on