I always put a chain around the chassis and then to the trailer , bolt the chain together at a couple places,
I like straps too, but the final safety measure is a chain,
plus the safety chain from truck to trailer
straps do come loose , so whenever you stop walk around the trailer and pull the rachet on the straps a click or 2.
get REAL straps 2-3 inch wide ones, not the junk they sell at K mart like a set of 4 @ $12
Trailers are limited to 55mph in California , but at that speed you get run over , but that is the law !
I normally try to stay at 62mph with a full trailer , close enough to legal speed and still safe