Never seen a bonnet spring up using genuine catches. The catch is actually from the original Ford popular, and is very simple and reliable. Some racing variants used much lighter over-centre clips and these were prone to coming undone, or rubber catches which broke, hence the strap. To my mind it's just a "period look" with no real function, and so to be avoided, which can actually cause damage to paintwork (very quickly if dusty/gritty).
Nigel
