What have you done and/or what would you do. Sport/street driving.
How much does a factory one weigh? I can turn flywheels down and have a place to balance them. If enough people wanted them i thought i could have a few done to have to turn around.
I think unless your Road Racing your car one weighing around 8-10 lbs would be good.
Just for off the line torque though. Once it's spinning I doubt it matters.
I have an aftermarket lightened one on my car but I cant tell a difference between it and the OE one.
Correct me if I am wrong (usually am)
but the lightened / balanced flywheel should help you rev up quicker,
but not actually improve HP. (Had a 10# one on my 98 8v GTi)
After I put it on, my 2.slo felt like a crotch rocket!
For the top end, you really want the momentum (rotational inertia).
A friend put one on a vr6 turbo, and felt like it hurt his pulling power.
The motor revved down so quickly, he was losing boost in between shifts.