In my opinion you can open the top from the drivers seat - especially if the frame is in good working order - but if you don't want holes in the top on the corners of the middle bow, you have to get out (in the snow in Wille's case) and 'hand fold' it as it is pulled back.
Osso, just curious, but if you had your top frame powder coated again after you inserted the (I assume) nylon bushings - did they hold up in the heat? There is no doubt that powder coating makes for a very durable finish, but when both primering and painting the frame I did a section at a time, then moved the bows partly so I could spray areas that didn't get coated and partly to make sure the primer/paint wasn't interfering with the top's movement.
Osso, I appreciate your compliment - especially from someone who has restored one of these cars to perfection. I can point you to the book "Original Alfa Romeo Spider" by Chris Rees. My first '69 Spider restoration is pictured on the Contents page, page 6 and pages 41 through 47. My clients had bought this car new. Although I suspect you're more interested in detail photos like the above ones.
Biba
Restoration of 50's to 70's Alfa Spiders
(How does one go about including a link to their website - for instance - since the 'atachments' won't accept html's?)