Sufficient enough for the car may be but if you end up in a roll and you some how fell out and the car ends up on top. Well...
Should really get a 5 point harness system.
5 point harnesses are only required for class 2 and up competitions, where flipping is a common occurrence.
These things are not built for speed, you rarely go more then 3-5 mph on the trails while rock crawling. When you flip grab the steering wheel, and hold on.
Unless your a fool not wearing your seat belt, your not going to fall out.
easy peasy japanesey
more pics:
muddin'