ronrathnow,
I didn't see what part of the country you're in and/or if you have traditional/seasonal winds/snow etc. We've used the "throw over" covers too and while they will keep the sun off the coach/travel trailer etc. they are fairly cumbersome to install and remove. Yes, I'll get arguments here but, lets face it, it doesn't really matter just how big your coach is, you still have to be able to get up on it, with that cover, unfold/unwrap/unroll it and carefully place it in place without doing damage to any of the roof components and or the cover.
If, you're willing to do that and, it satisfies your quest for a cover, by all means, have a ball. But, just a note here. One of the reasons, most likely not the most important one but never the less, a reason for this type of cover, is to keep is somewhat clean. Well, if your coach is left uncovered for any length of time, it gets dirty and dusty doesn't it? Well, that covers going to get the same dirt and dust. But, depending on how you remove the cover, when it comes time to re-install it, you will transfer all the dirt accumulated on that cover, to the coach and in fact, will be in between the coach and cover. Again, I'll receive flack here but, I've seen it first hand way more than once.
If you have one and when it comes time to remove it, if you fold it in such a mannor that it will trap the dirt etc, in between the folds and not put that dirt onto the coach when re-application is done, then you're one-up on that. It's still not an easy task.
Covering an expensive coach with anything is better than letting it sit in the elements. We've all seen very expensive coaches sitting, rotting in the sun, day after day, week after week, month-year etc.
I don't know about you're local codes, abilities, desires etc but, if I may, I'd like to suggest on kind of like the one we just installed/built. It's a "tubing/tarp" style cover. It's anchored to the concrete and is able to withstand fairly substantial winds, (already tested). We've got a total of about $1400.00 wrapped up in this cover. We purchased all the components from a local company and erected it ourselves. The entire build, start to finish, took us about 3.5 hours. It's 18' wide by 40' long and 11' high on the sides. It was 12' high when we built it but, after standing back and looking at it, I decided it was too high so, my wife and I shortened the entire cover in about an hour. Way better.
We've got plenty of room for the slides to stay out if need be, and I can still walk around it. I've developed a "curtain" for the front to keep the UV and other elements off. It slides right out of the way when it comes time to drive the coach out from under the cover.
Now, all this of course depends on your area, codes, climate, etc, and if you've got the room for something like this. But, for not all that much more than a "throw over" cover, you'd have your drive-under one. Just a suggestion here. Take care.
Scott