It sounds like Tango is on the right track. However, I'm wondering how his braces work against lateral forces. I assume there's more to the picture than pictured.
Have you been able to look up the spec's on your roof? Do you know how much weight it can take before any mods?
Most monocoques are fiberglass. Is yours? (Sorry, I can't tell by the pics.) If so, I'd be very careful about punching through it due to the danger of cracks from stress and movement (especially with square shaped or large holes).
Have you considered support beams inside? No [extra] roof penetration, just more material, effort and money - plus a bit less headroom (with some pretty spiffy fabrication on the curves).