Sean, not sure on what these guys are selling you but on the exposure thing...since you mentioned FX, think of it as two different contracts, the full contract is worth say $100k of the underling that would be your 400% exposure...in the case of the 200% exposure you would be controlling only half that amount $50k of the underling...so each contract that you buy on the underling would be worth 50k as appose to 100k...it would be the same as if you would open an FX mini account or a full size FX account. Read the fine print...
I would be more worried about someone investing my money in that kind of an instrument.
Best of good trades, Spike