do I dare do the same post in the same day?
take a look at the two-ladder scaffold here
note that the boards that are under the ladders has a sheet of 1" foam on the side next to the shell. If you can find a 12' non-extension ladder, that would be perfect. I had these ladders from doing siding on my house--they are pretty cheap, regardless.
BTW, if you can find one of those articulating ladders, the ones with the three hinges, not one hinge, if you fold the hinge at one end to 30 degrees, it makes a single-ladder scaffold that fits nicely to the shell and allows you to reach things like the vent covers, but it doesn't extend far enough for you to actually get "up on top." A single straight ladder on the side does not allow you to reach the vents.