I recall someone making a lift top that used hydraulic RAMs. Might be out of yer price range but it might be something you could consider.
I'm not sure you'd want to drive down the road with yer top lifted. The airflow at speed will test yer engineering and fasteners to their limit. Even with my hatch slightly up on my aero cap, I have to attach metal straps/brackets to lock it in place. Bungee cords do an okay job but there were times the air flow really tested the bungee cords. Just something to consider.