Here's the part that seems to fly over your head- Never did I say heavier flywheel is quicker, the point i'm making is that flywheel weight isn't a handicap when it makes the process more efficient. You say get the lightest flywheel you can find, I say you can get a flywheel that's too lite.
One thing a flywheel does is act as a heat sink for the clutch disc, as does the pressure plate ring. It's a given that something needs to slip for a bit or you will either bog the engine, blow the tires off, or break parts. If part of your launch plan includes controlled wheelspeed, some of that slipping duty is shared by both the clutch and the tires. Because in this case the clutch doesn't have to do all the slipping that's needed, you can get away with a smaller/lighter flywheel and clutch. And given that most all clutch development in the past for cars like ours have included wheel speed as part of their launch plan, we now have flywheels and clutches that are too lite to handle the thermal load of doing all the slipping necessary by themselves.
Ever see one of Rob Youngblood's flywheels? Pretty much the minimum amount of mass there to get the job done that it was designed for, and one thing that they are not designed for is to do ALL the slipping that's required for a dead hook radial friendly launch. Same goes for the typical aluminum flywheel with a bolt-in "heat shield". In that case you have two different materials that expand at different rates. They may be flat at room temp, but the shield gains temp quicker than it can pass it onto the aluminum. At some point as temps rise the shield begins to warp, which causes it to lose intimate contact with the aluminum, which in-turn further reduces the aluminum's ability to act as a heat sink. It's a downward spiral that damages the clutch. Thicker heat shields help reduce the warping, so do segmented inserts. Something that eliminates the warping altogether is one piece flywheels with enough mass to control the temperature rise. Since an aluminum flywheel without an insert isn't really practical, steel becomes a simple effective solution.
You can run a sintered iron disc with a 'tamer, I have for years. When you run radials, it makes logical sense. I currently have a Ram dual friction disc in the car just to gather some data, seems to be working with the radials. It's seen 8600 quite a bit, organic side hasn't objected yet. Steel flywheel, nod iron pressure ring.
Grant