[santos the ranger]

I also posted in the Volvo car rack forum section but thought I'd drop the same question here hoping I'd have like twice the chance of getting it answered! Does anyone have experience attaching the Thule 554XT surfboard rack to a 2004 Volvo s60 with a factory rack that is made by Thule Racks for Volvo? Leaving on trip with a tight budget and hoping to spend as little as possible. I do want to lock the surfboards though, is this possible?