Way cool!! Very nicely done!
How did you determine the initial alignment/placement of the hinges?
What do you think about rigging up something to hold the targa top to the trunk lid? So with the trunk all the way open you could drop the top down vertically into some j-hooks/catches at the bottom and clip the top to hold it in place. That way, even with the top stowed, you could still have full access to the trunk/engine bay.
For even better engine access, the engine lid could be attached to the trunk lid... Sorry going off on tangents.