It's a thicker bolt and it comes with a huge reinforcement plate thing (ie, large washer to put under the sheet metal)... that wouldn't make it stronger? You can't just put it in the same hole that the standard car's anchor was in, you have to drill a thicker hole to accomodate the thicker bolt. It's the hook on the vest that is thicker, I hope... I heard offhand once that it wasn't the car's standard anchors that failed as the dummies got heavier when testing the tether anchors, it was the hooks on the anchor strap on the carseats that failed...I don't know if things have changed since then but it's interesting.
At any rate, plenty of people have been tethering seats well above the stated limits for years (I'm saying, the regular people who think their coscos should harness to 80 pounds, so it's misuse, but still), and the same cars in Canada have the same bolts that have always gone to 48 pounds and now are going to 65 pounds, so I'm not in the least bit afraid of my Regent tether failing even if I use it over the top listed weight limit