I think weight has something to do with it, but here is my take. I think it has more to do with gear ratios to be successful with an aluminum flywheel on the street. That includes the first gear ratio not just the rear gear and tire roll out. I had a 2.78 first with 4.56 rear and 29" tall tires and when I switched from a 30# steel to a 15# aluminum, I was surprised that it drove so well. I had no trouble at all driving away from a stop "normally". At the track the aluminum is faster as long as you can launch it correctly (adjustable clutch tuning). Now if you have a 2.32 first gear and a 3.25 rear, that combo will not work well. You can't "ride" the clutch a little to get it going with a lightweight flywheel. And if the car was heavy or light it would make this better or worse on opposite ends of those two examples.
I have a friend that drag raced an old T-bird for 30+ years. It was a lightweight chassis car, had a 351 CI small block with less than 600HP and a lenco 4 speed. That car hauled ass, he never changed a thing over the years other than playing with the flywheel. He had a 32# a 22# and a 12# flywheel. He didn't have much torque, and a "hard lock" clutch... the 32# would spin the tires (14x32), the 22 worked the best, and the 12# would dead hook and then bog. If he had an adjustable clutch, the 12# would have been the fastest. The car ran 9.07@150+ with a 9.2 deck SVO block, old FORD Motorsport A3 canted valve heads, even had a single 4 FORD A351 cast intake and a 750 DP carb, was standard bore and stroke. All the BBC Chevy guys that had big inch BBC's had trouble running with him. He trailered a lot of dragsters and was a lot of fun to watch.
