http://www.rei.com/product/732929
I'm not the first on the site to purchase one of these but I was asked to post if my mounting scheme worked. I think it did. I should point out I did not get this as shelter from torrential downpours, but I think it would do OK in that regard if it's staked properly. We mostly needed an awning as protection from the constant winter drizzle of the Pacific Northwest. We wanted a portable awning that could stand up to some mildly nasty weather if needed but that would not require drilling more holes in the van and that wouldn't take up too much storage space. The awning works pretty well mounted over the cargo doors. I haven't figured out how to mount it over the rear doors yet.
My solution for mounting the awning to the van was pretty simple. I use the large carpenter's alligator clamps found at almost every hardware and home improvement store. Mine are Pony brand which has been around forever and are really well made. Don't remember where I got them. The clamps fit into the gutters pretty nicely. A small piece of rubber or foam between the awning pole and the rain gutter wouldn't be a bad touch as long as it didn't reduce the friction. I'll use at least 3 or 4 clamps, depending on the weather.
One problem is that if you place a clamp on the gutter above a door then the door won't open. Enough of these and you could trap someone in their van... till they opened a window.
The other issue is that there is a gap between the awning and the side of the van. From 2 to 4 or so inches, depending where you measure along the length. Neither of these are big problems for us. The gap problem could be overcome pretty easily with a two by ten foot length of Visqueen and some clothes pins. I could see pretty easily coming up with some simple pieces of wood or flat stock that would clamp to the gutter instead and move the edge of the awning more inboard. Part of our reason for the awning is to cover our cooking area so I'm looking at the gap as a feature not a bug. We'll see how it goes.
Obviously I'm going the low tech/KISS route with this. Overall I think It works pretty well. I'm looking forward to trying it in the field. It should work with the penthouse top up or down.
The awning itself seems well made. It's a little more complicated and time consuming to put up than a backpacking tent, but nothing horrendous. I'm sure once I've done it a couple times it'll just take a few minutes. What I really like is that you can have the outward edge of the canopy up on poles or staked down to the ground. When down you can lower the wings to create and fairly weather tight space. In the down position I'd probably put a towel or the like over the corner of an open door to prevent any wear and tear on the fabric. The fabric would rest on the door when I had it open.