[niles]

chris;
Both have pros/cons. 30lb iron stores energy and smooths the engine out, cluth will be less sensitive to stalling, less lurch when lugging engine, etc.
Alum rev faster, when you hit it, more Hp going to wheels and not building inertial energy as it spools up.
I put an alum in my stoker and like it. I like the way it jumps when you blimp it in neutral; but the neatest sound is when you shut down; the engine spins for about one piston compression stoke and this suddenly stops. Key off-whomp-silence; very cool!
gn