Originally Posted by
Caffeine Fiend
We bought a heavy duty car cover for my wife's MX5. It sits outside also and we wanted something to protect it also from potential hail damage. Not sure what the situation is like regarding hail in Bris, but in Melb it can happen up to couple a of times a year with enough intensity to damage/dent paintwork. It wasn't cheap but it's still cheaper and less painful than making an insurance claim to repair hail damage.
My advice would be to look for a cover with a soft lining (doesn't necessarily need to be hail resistant to offer that). The other important thing with covers that have a soft lining is to keep them out of the weather when not on the car, so the lining doesn't get wet and get grit etc caught in it that can drag across your paintwork when the cover is next used.
As you have Opti-Coat, you'll have better scratch resistance against this sort of thing and also potential rubbing of the cover against the bumpers/guards etc in high winds. It's not infallible though and the most you can do to protect the inside of the cover from getting dirty, the better.