I have four, closed hooks, looks like the end of an alxe strap, bolted right to the 2" x 4" frame. I reach under with a web racket - catch one hook to the floor tie down and the other to the installed chassis hook, all four corners. Just tighten and go. Don't look pretty, but it makes trailering real quick/secure and easy. I never liked squeezing down on suspension parts, like alxes or a-frames.
That's my 2 cents.