yeah, i'm calling that part the tonneau; i've also heard it called the clamshell. if you remove that part, along with the soft top, motors and engine cover, you lose a LOT of weight (= better performance) as well as let more air at the engine for cooling, improve engine tone and make access for maintenance easier.
you can't drive around with all that open, however, so you would need to fabricate a panel that replaced the clamshell panel as well as extended forward and terminated just behind the rollbar (have the front of it roll down and seal against the engine bulkhead). it could be held in place by the spinlocks, and be vented to let the engine breathe.
it would certainly have a 550 spyder look. further, you could add speed bumps if you liked. you would also need a speedster style roof similar to the one on the new spyder.
regarding the hard top, once you hand the rear panel fabricated you could bond a hardtop to it with a vertical rear window to get this look:
linky ...