I'd say you are reading a bit light.
Most of the guys I know that have weighed their SV350 bikes are in around 350-375 lbs.
What's the bike stock? Around 400?
Takes some doing to drop 100 lbs. You usually have to go the whole way, glass tank, fenders, seat, alloy wheels, no battery, lightweight exhaust, alloy rear sets, absolutely all unnecessary brackets etc removed, alloy clip on's, electronic tach, even the lightest tires you can find of suitable size. You have to get down right anal, you can say to yourself...oh this only saves 2 oz, it doesn't matter. Do that a few times and you are giving up a pound.
I've made chain adjusters for my bike, brake shoe cams are drilled hollow, I've made alloy brake rod adjusters...stuff you don't think matters but it adds up.
With FCB where you don't have to spend a ton on the engine, spend it on the chassis and get it as light as possible. Can get expensive though.
Build a FCB chassis within the rules but as light, and with as much attention as if you were building a MotoGP bike...and I think someone could end up with a quick, very good handling, fun to ride bike.
Since my bike weighs about 200 lbs. I'd give a 350 40 lbs extra for the engine, and 40 lbs extra for the chassis....that should make a 280-300 lb bike possible. Put on a rider under 200 lbs and you'd have a package that could run up front.
JohnnyB