[invictusmaneo]

Most articles say the top is two pieces, but I saw one that also purported to quote M. Gales saying it would be three pieces.

I don't think the top is stressed (but I am most certainly not an engineer). If you read the service notes pages on how to remove the top, it doesn't seem like it. It is bonded on, but not apparently using the same stuff as the chassis, and I think you could basically cut it off with piano wire, once you remove the trim parts. I think that gives credence to the idea that as long as the roll bar remains in place, there isn't any significant loss of rigidity, and that it was designed this way from the start. British Racing offers a carbon fiber replacement roof Lotus Evora Lightweight Carbon Fiber Roof

That doesn't necessarily mean it doesn't add stiffness. It probably isn't critical, but I bet it is structural. Much like the center shear panel (not the diffuser) on the elise was considered structural even though you could unbolt it and drive away wihtout it on if you wanted

 

[invictusmaneo]

A quote from the Lotus Press Release when they first unveiled the Evora:

"The Lotus Evora employs a composite roof as a stressed structural member to give an exceptional vehicle stiffness of 26,000 Nm per degree, thanks in part to the seatbelt anchorage frame's secondary function as a roll over structure, and partly because the high-tech composite body panels are stressed items. However, despite this high stiffness, the complete chassis and modules weight just 200 kg (prototype weight), helping to keep the weight of the whole car to just 1350 kg (prototype weight)."


Unfortunately I would never cite Jalopnik as a reference, but I don't have time to dig up the formal Lotus Press release-they have it quoted in full:
The Lotus Evora Weighs A Ton...And A Half


Not arguing, I think it is all in interpretation of both pieces of information. I think Gales is right-no rigidty will be lost and they may compensate with some additional bracing in the rear roll hoop/seat belt anchor or something, or have redeisgned the chassis to compensate in addition to the other changes to the tub.