There is a rule somewhere ( I can not quote it at this time) which clearly states there is to be no lose items etc. This includes tarps which cover loads and the ropes straps etc which hold down a load.
My former days working as a mechanic in a truck yard, there was a great deal of time spent in securing the old green canvas tarps on the semi's as well as the ropes, we even had a guy who had to check it.
I believe it is fair to say that your average CT with a cover falls under this requirement, so having your cover billow up and down as your drive could be seen as a lose load cover by the transport authorities.
How it is secured is not relevant, as long as it is secured appropriately.
I fitted some webbing straps and buckles to mine which work well, cost me $50 at a canvas firm.