My first box opened from the nearside only making it very difficult to reach the clamps at the hinge side, if it had u bolts i don't think it would have been possible, luckily i had bought from the roofbox company and was able to swap it for one with dual side opening, problem solved. Must say the roofbox company are really good to deal with, you have 90 days to swap your box and they are cheap, will post photos when it stops raining ☺
Chris