Your letter reminds me that those horrible ‘H’ bars used to lift up the roof and hold it in place, that have already been around for more than 27 years!
Every year I see at least one pop-top caravan being towed with the roof lifting at the front. This is due to the low air pressure area (or vacuum) generated by the caravan being moved forward fast.
The problem is usually because the roof has not been correctly secured with the overlocking ‘tooth’ engaging a side bolt (see picture).
Over the years, safety straps and wing nuts have been added to prevent the ‘H’ bars from allowing the roof to lift. Straps are the sure-fire way to secure the roof.
If your caravan does not have these, you might seriously consider doing this modification.