The use of an aluminum flywheel in a street driven car is not a problem. When you stated in your earlier post that you plan on drag racing this thing, you will see why lightening up a flywheel in a turbo stick car is not a good idea. If you go with a spec unit and a spec clutch, which is heavier than a factory unit, you might not see as much of a loss of momentum on launch, but you will def see what I mean. The rpm's will fall very quickly on launch, and that causes the turbo to not be in it's rpm for 'spooling' and you have a pig of a launch. An aluminum flywheel is not going to make your car faster, I couldn't even tell the difference in mine on the street, but when I went to the track I could.
See, I have a different problem, my car makes 500+ ft lbs of torque at 3500 rpm's. You do the math on a steel 25lb flywheel and the heavy spec pressure plate, and it makes for tire frying torque. So I went to an aluminum flywheel and the car picked up .15 in the 60ft. I have a customer with a 4.6 n/a car, and he insisted on an aluminum flywheel, because it 'reved quicker', well he can't get a launch without bogging unless he leaves at 6k+ r's.
I wanted to experiment with the new spec lightweight aluminum pressure plate, it has a small steel insert like their flywheels have. I put it in my race car, only change I made, and went out to the track. put it on the two step, nitrous on, and popped the clutch at my old launch rpm of 3600. Well, it fell on it's face and didn't like it at all. bogged, and on nitrous, that's not a good thing. I thought about it and at the next race, I put it up to 5600 rpm's and launched it, the pictures in my race car thread are the result. it falls nearly 2000 rpm's to the max torque and then takes off. before it wouldn't even fall, it would just launch. much more controlled. Did I see any better et's? nope. just spent money. It did however improve my 60ft once we tamed it down, but in hindsight, I wish I would have just stuck with what worked.
Now, in conclusion, and I am kidding if anyone really read all of this, but my opinion is, if you want an aluminum flywheel so bad, throw it in there and make it work. Lots of people do it every day. Is it optimum? Who knows, you haven't made the first pass to even know what the car will do yet. I have found that making too many changes without watching what each change makes at the track or on the dyno just makes for a car that is unpredictable and becomes a problem child. jmho. Drivability on the street, that's not much of an issue, just rev it up a little higher when you take off, and there is no slipping a spec clutch, you'll have one chattering pos if you slip it from new. dump it for the first 500 miles, talk to Markcore on here, he just got a new one in his car.