Hi Tim
I bought the Hamilton net on Graham's (GlutenFree) recommendation - couple of things to clear up - 1) it is not a stretchy material, it is a solid weave that allows a car cover to be anchored down to avoid billowing or loss of the cover and 2) it is a massive faff - it needs to be fitted perfectly which takes practice and has to be looped fully under the car in 3 different locations, meaning crawling around underneath is inevitable - not desirable when its lashing down with rain!
You also need a very robust cover underneath it as the net inevitably rubs the cover between the car and the net, putting either holes in the cover or slight rubbing on the car (made a couple of rubs through the paint on my rollbar).
I have tried every iteration of car cover for trailering my Westy now and the only one that works 100%, doesn't create drag & is easy to use is the cockpit tonneau. Yes the car gets wet (but less so than if you were driving the car through the weather), easily solved with a quick chamois, but the tonneau keeps the interior bone dry, is easy to put on and off and doesn't cause huge amounts of drag.
I did the same thing as you, put a post on here, tried all the things that were suggested before realising one of the first suggestions (think it was Terry) was the best. So hopefully you can benefit from my experience!
My Hamilton net is available should you wish to try that route but I strongly suggest tonneau is the way to go.
Cheers
Barny