To install the harness properly you will need something like this for the shoulder belts. www.sidexsideoffroad.com/RangerHarnessBar.html Then I would recommend Crow harnesses. Either 2" or 3" wrap around shoulder belts and 3" lap belts.
Yeah the crossbar helps with some cost. Unfortunetly the Ranger, Rhino, and Teryx haven't implemented this. Good thing however is that it's a simple add-on. Here is the Ranger we played with a while. You can see the harnees bar is out of the way and fit's nicely.
The problem with shoulder straps are, that when they are mounted too low they can cause spinal injury. Since I'm 6'2" and my daughter's are shorter it is hard to have each seat set up correctly for each person since they will be driving / ridding also. So I have mine in my Ranger and CJ mounted high, I have them to control the forward movement of the body. The lap belt will hold you in if you are up side down.
General safety is different then competition and everyone will have their own views.