Yes I guess I should have made it clearer in the guide (now amended) but I did use really large thick washers on the underneath to make sure that in an accident the bolts should not pull through.
If you think about it all that holds down the 200 seats is 4 bolts and only 2 of those have spreaders on.
So in theory mine are more secure in that they have 10 bolts. But if people really want them to be extra secure then get the welder out and weld the panels in place. I decided to bolt in so I could remove them again should I want to. If you weld them in then there is no issue concerning safety (unless you weld like I do!) !