I've had a few lightweight flywheels in the past including toda, fidanza, and a synergie segmented flywheel, yes revs certainly do rise and fall quicker out the 3 I've tried the synergie was by far the best.
Don't like them. call it torque (to me that's what it feels like) or inertia which in a way creates torque, the car does not have the same pulling power (similar to what a diesel car does have if you like) seem to lose that kick back in the seat affect.
So as MrB rightly says the way to go is have a souplike of kg skimmed off your stock flywheel then you sort of get the best of both revs without losing that midrange pulling power.
That's what I had in my last track car and that same flywheel will be reused in the new project too as very happy with it.
So if your hell bent on getting one pete I would definately get the synergie fly as opposed to others, but 30 squid for a skim and you'll have even better and put the extra you save towards a good clutch or something
In association with
Torque Of The South Motorsport
Nissan Performance & Tuning Centre
Forge Engine rebuilds to specification
Body Restoration, Fabrication, Repair
Paint refinishing facilities
Ecu re-mapping-Performance upgrades
Auto Diagnostics, Injector cleaning
Race & Suspension setup
General Servicing, Mots, tyre fitting
Full workshop facilities