I have on many occasions have advised that  a carport with a concrete floor is the best way to house your expensive van.

I tried to save a buck & went for gravel floor and the best silver tarp that I could buy.  Only halfway there.

The good silver tarps last at least 3-4 years in the Southern Qld climate and another 2 years if you put a piece of shade cloth over the tarp.   Good for hail protection too.  I use my annex floor for the extra cover.  It has lasted 20 years!  Of course all tie down points (in my case loops through the hollow section van chassis) use shock cord.

To help with the temperature in the covered van, tie three polystyrene boxes across each end and one on top of your Air Con unit before fitting the tarp & shadecloth.  This provides an air gap and stops the tarp from rubbing on the van paint.   Also good for hail protection.

To finish off, I throw a tie down across the covers just behind the AC to stop it flapping in the wind.  Essential in my experience.  Another one in the front would be good too.

Sure it takes a bit of time to set up but its worth it to protect your investment.     Yep the commercial covers look good too, until they don't!

edit ... BTW, I find many of ALDI caravan  accessories are not up to standard.  Have dumped a full set of their privacy screens & two annex floor mats. But their 10/20A 'switch' is good value.