First off, if all you read is this first sentence, LEAVE IT ALONE!!!
Now, my reasoning. The coupe is designed to use the roof panel as a structural piece, and so needs to be there intact. It is needed to keep the whole uni-body construction ridgid. When you cut it out the integrity of the structure is decreased. If you look at the weight difference between a 95 Targa and a Coupe you will find that the Targa is about 100+ lbs heavier. Granted the removable top is some of that, with the latches and such, but not all. The engineers have had to beef up the whole lower body, on the targa, to maintain the ridgity of the body without the structural roof panel.
On every automobile that has ever been produced in a coupe and convertible (targa) you will find that the coupe is lighter, for these reasons.
Look at what you are going through here. You are having to ask questions about a major modification on a car, think what it will be like if you had to sell it. It was a perfectly designed car intended to be left intact. Now it is a FREAK. It is hard for me to say this about a NSX, but it is true.
If you want a targa, find a clean 95 (first year for the targa) and buy it. If or when it comes time to sell it you will be able to sell an original targa a lot easier and for more than a modified car. Yes, you will have to spend more but think of it as an investment. If you can't afford more, buy a coupe. $28,500 is a lot for a modified car. Kind of like a salvage title car. That is another story in its self.
I find that my coupe is quite nice. No wind noise, no water leaks, don't have to put the top in to lock the car up, don't get my bald head sun burned, don't blow my wife's hear, don't have people stand up in my seats, don't have people wanting to use my car in parades, I have never dropped my top, I have never lost one of my favorite hats and had to turn around to get it.
Be patient, it took me about a year to find a clean 91, and got it for just a little over $20k.
Hope this helps.
Brad