Whre are your belts actually secured? It looks as if they are bolted to the floor in that pic, unless theres alot of excess belt hangin to the floor.
If they are bolted to the floor, then yes, it shoudl be changed. It doesnt look as if its so much that the bar is too high, but that the belt holes in the seat is too high.
You could also look into buying a harness bar from MDC. It might be able to be used in conjuction with the cage.
Either way, the shoulder belts should never be secured to the actual floor.