I don't know how this usually works but what I want is the option to buy BTC at $X worth of PTS any time until some date from (say, Dec 31 2014). Escrow would hold the maximum amount we agreed I could buy until that date. I'd pay escrow and other party up front.
If I can hedge against sudden order-of-magnitude jump in BTC value (I've been through 3 in 3 years...) I would allocate a MUCH higher proportion of my holdings to PTS/AGS.