In addition to people watching that is only rivaled by the county fair and major airports, Harbor Freight has some nifty little D-ring anchors on sale right now for $0.99. I paid something like $5 for what appear to be identical units at Home Depot over a year ago for Grocery Getter v2.0:
I picked up a few pairs just to have around. Never know...
I dunno, and I'm not real good at the maths, but I can vouch for them being stout enough to hold down a fully loaded 60qt cooler and (2) medium sized, also fully loaded, Action Packers over some pretty terrain at a high rate of speed
These make great tie-down anchors for smaller tie-down straps (motorcycles, etc).
If you want them to be stronger, solid-weld the spot on the D where the two wire ends meet (under the strap). I think they are only spot-welded, if welded at all.