The planes I fly you can see the tops of the wings and tail from the cabin, so I just have to send my co-pilot back to check it out. Though if it's snowing generally I do everything I can to get off the ground ASAP, and if you get the clearance before you fire up, it's not hard at all to get off the ground in under 5 minutes.
As for the Van, I've only flown one a few times, and only as a ride along so I don't know what their requirements are. But I would think you'd be able to see the top of the wing if you opened the door, stood up, and looked back.