Didn't say it couldn't physically be done. I said to get it approved/engineered in QLD to make it road legal would be next to impossible.
The handling is the least of your worries. The roof/windscreen make up the main structural rigidity of the vehicle. There is a reason why convertibles weigh 30-60kg more than the equivelent coupe/sedan as they have to make up for the structural loss. Hell drive a factory aero-top Supra with the roof off and feel the whole car twist and vibrate; and that's a car that was engineered properly by the manufacturer.
You wanted advice, we are giving it to you. If you want people to blow some smoke up your ass by saying "Yeah man do it, piece of piss, just chop the roof" then go on Boostcruising.
As said above. You want a nice Nissan convertible cruiser buy a Varietta and drop a turbo motor into it. Will also look a hell of a lot better.