I have a Nissan X-trail with roof rails, looks like this:

[![x-trail](https://i.stack.imgur.com/bFxM9.jpg)](https://i.stack.imgur.com/bFxM9.jpg)  

(source: [cloudfront.net](https://d1qrsrfok4yvrh.cloudfront.net/eyJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjUzNiwiZml0IjoiY292ZXIifX0sImJ1Y2tldCI6InMzLmljcy1hc3NldHMuY28udWsiLCJrZXkiOiJtZWRpYVwvaW1nXC9jYXJfZ2FsbGVyeV9pbWFnZXNcL0U5M2lqZEd0UUJWUDJMVTNIbnJILkpQRyJ9))

I need to transport 2 of these:

<https://www.ikea.com/gb/en/p/melltorp-table-top-white-90280096/>

I really worry this is a silly question, but I've never used the roof before - is there anything to worry about with regards to transporting these on the roof?

My absolute fear is them coming loose and hitting the car behind me. Assume they're strapped down super tight with ratchet straps (unless there's a better way) - should the nature of these desks -i.e. super flat, cause worry, about how the wind will interact with it?

Is there any top speed I should have in mind - would highway driving be problematic?

Much appreciated for any guidance.