The 100lbs of downforce at 100mph for the Exige is no more draggy that any number of cars that produce 100lbs or more of lift at the same speed. It's just a lumpy, scoopy shape people.
Now THIS is how you go 280mph on 200hp or less:
2006 McLareghini Bugatterrari, Storm Titanium... <mods> installed: air horn, Scroth 4-point ASM harnesses, Sector111 halon extinguisher and mounting bracket, Von Hep exhaust and rear panel delete, Pagid brake pads, red Volks CE28n wheels, Toyo RA-1 tires, Nitron SA coilovers, Sector111 (WorksBell) quick-disconnect steering wheel kit. awaiting installation: Scroth "pull-up" lap belts, Sector111 RTD Brace, Tony's heater bypass mod, and dropped steering rack mounting plates. </mods>