Hi Michele -- just saw this thread and thought I'd comment.

I use the sheet over the crate in my vehicle whenever I have Ellie in the car -- parked -- for an extended time. Most of the time it is on training days at the field when I don't want her firing off at club members and their dogs as they pass by my vehicle. It works extremely well for me -- although there is the occasional walk by that is a little too close for her and she will fire up until they are out of sight. (I cover the crate except for the front of the cage which normally faces out the back of the vehicle -- and I usually have the back open for ventilation.)

When I am out running errands or something I usually look for a more remote parking spot as I know that Ellie can scare the heck out of an unsuspecting person coming too close to the parked vehicle. But with that said -- to me she is doing her job protecting the vehicle and there is always the person that will park right next to my vehicle even though I have obviously picked the furthest spot!

As for barking while I am driving the main issue I have there is cats -- seeing one will really set her off. In this situation I have a throw chain that I keep in the console and all I have to do if she doesn't quiet when I give the command is to pick the chain up and rattle it in my hand. Initially when I first started to use it I would actually toss it back toward her crate --it would get her attention and for the second she stopped barking i would say "quiet -- good quiet". Then usually the offending kitty is out of sight and she is settling.

Just some of my experiences in a similar situation as you and Cato. Ellie is my first working line too -- it is an education isn't it.

Update...
After trying what I thought was an sheet and failing miserably, I remembered another one...That's the one.

He did very, very well and we will do this and bone for some time. I think this will coincide nicely with his other social issues.

PS. Check out my thread on keeping your latches clean...I've had a freakin DAy, I'll tell ya...