Kevin,
Lightening the stock flywheel has limits but a 20% loss of weight should not cause a strength issue IF its done by a real pro, and then re-balanced. Most of the aftermarket flywheels are drilled for both 2.0 & 2.3 engines. Check out the Mini stock sources, Racer Walsh, Esslinger Engineering. Tilton (Big Bucks but very reliable),Centerforce . I was running a 2 disc non-sprung aluminum that weighed half the Stock flywheel & clutch package weight. (14 vs 32 lbs) It caused some problems with the flywheel surface and it turned out to be a major issue because of the lack of a Steel friction ring on the flywheel. Later, went to a Lightened Steel Fly, 2 disc non sprung discs. These don't work on the street, no give in the clutch hub, all or nothing at startup from standstill.
If you've got the low end torque, the flywheel weight is less of an issue for street driving.
Keep tweaking that car, you'll be surprised..
Pintosopher