So, I'm looking to put a four point harness in my gp2.
There's a nice one that's plug and play from Schroth that would be perfect.

https://www.schrothracing.com/tuning...t-pro/qfp-mini

The trouble is, it's designed to attach to the rear seat belt buckles of a normal mini.

Has anyone added a harness the their gp2? How did you go about it?

 

Your GP has the holes for the rear seat belts like a normal mini, you would have to buy the rear seatbelts and figure out a way to make them come out of the GP back which is easy. if you have questions let me know and I'll figure it out for you.
Better yet you can get the kind that will strap around the strut support bar that your GP has and that problem is solved !

 

I didn't want to mess with installing all that in the rear, and removed the rear bar so I could carry stuff. So I just currently use the CG Lock on the stock belt and it works great.

 

Don't do that, it is not engineered for it. The rear strut bar is only held in by a small M8 bolt (on unknown tensile strength) on each side. The bar itself is actually very strong, but the fixation is the question mark.

 

The other issue is that the harness is typically routed through the space between the headrest and the top of the seat. The GP seats don't have a harness pass through.

 

I also just use a CG Lock for Auto-X and fine it works pretty well. Of course, not as well as a harness but great for the price and ease of install.