I used this to tote a box on top of my two luggages that were strapped together using the Travelon Multi-Bag Stacker, Black, One Size. It held the box tight on top of the luggages even through bumpy door ways and elevators.

It held everything in place and I didn't have to keep looking back to see if my load was still in place.  I only really use this to and from check in or from baggage claim to my car so it's fine for those short trips.  It's very secure as long as you install it correctly.  The hard sections that help support the bag is great!