The problem with ground anchors (I think) unless the chain goes through the frame all a thieve has to do is remove the rear wheel. I use a single bolt in sold secure gold pivoting anchor the theory behind the movement is if attacked with a hammer etc the anchor will move slightly which will help deflect any blows. But the reality of it is I could probably break out any anchor with in a few minutes with the right tools albeit noise would be created...I'm not a thief but I do construction work so I know about concrete strength etc I have also broke out a couple of anchors of my own when I've moved. If you can you should try to have the anchor between the bike and the wall side to reduce exposure to attack, also try to keep the used part of the chain off the ground to make it harder to break. My chain is that big it just fits through the anchor with a tight squeeze I don't think that you can get one that is much bigger, if you believe all the manufactures hype it cannot be cropped.