You're going to need to stand it off from the card by say at least 10mm, otherwise the air will not flow through it. Some dowell and hot glue/silicone rubber will do the job.
:bow:
, it will stick owt to owt or your money back, with the bonus advantage of absorbing vibes. I said hot glue cos that would do the same job, but thinking about it you'd have to be careful with gluing to the back of a graphics cards, cos if you'd have to be careful you don't pull any surface mount resistors off if you need to remove the fan. Silicone rubber would be ok though I would have thought. Usual discalaimers apply btw.