John IMO, with the torque that these engines produce even at low RPM's, I dont think that flywheel weight would have much issue of the engine stalling except possibly on a N/A engine with real radical cams maybe. The flywheel that I am running is only about 7.5 lbs and I dont notice a single bit of differance between mine and Jakes old iron one. I can let the clutch out pretty aggressively without any throttle from a stand still and my supra wont stall (and no the clutch is not slipping, easily lights up the tires at will in 1st and somewhat 2nd gear, and can cherp'em into 3rd if I get the shift just right)....
Now will the engine bog, yes and I will agree that flywheel mass does assist in the launch but the other thing to thing about is not what the mass is but where its at or how far from the center of rotation it is. Remember that 10lbs. @ 5" from center of rotation will have far less effect then 10lbs. @ 10" from center but its still only 10 lbs....
When I designed Jakes flywheel, I left quite a bit of mass out towards the outer edge. Taking out that some of that material will have quite an effect on inertia but will only reduce its weight by maybe 1.5 to 2 lbs. at the most.