Rovers North Rock Sliders

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Just got a set of new Galvi sliders. Waited a couple of weeks with high hopes. Was told that they are very popular. Arrived on Thurs. This sat I unpacked them from the copious amount of protective packing and bubble wrap. Total parts .... 2 rock sliders, 2 mount brackets, small bag of grade 5 hardware...... no instructions .... nope none.....
Hey , I own a Series Rover. I can fix anything. just 4 parts ...right?
After orienting the sliders to the proper side I attempted to bolt on the rear mounting bracket........ bolt goes in..... bottoms out at less than 1/4 inch. The extra metal welded onto the slider is tapped and clean of galvi. the remaining metal behind the hole is not tapped.... not tapped , nor is it drilled.... Hmmmm very useful. So glad I bought pre made rather than make myself. I also notice the slider will not fit straight with the body work, It hits the door post metal.
Any of you guys have this problem? I googled and found no help, One would think a set of install instructions would have been posted .... but I found none.
Another weekend wasted....