I can no longer edit the original post but just wanted to post a follow up in case anyone is google searching and stumbles across this:
Using the card indeed works, you need to have a can with a proper diameter so that you can place the card in the position of the "1/4 Wave" value when using this calculator; »
www.csgnetwork.com/anten ··· alc.html ((e.g; 4 inch can needs to have card placed 1.72 inches from the rear of the can))
The position of the card inside of the can needs to be at a proper angle as well (not pivoted/leaning etc) so take your time and make a good slot to fit your card into. I used the punch on a can opener for my initial hole, stabbed a screw driver in to make a hole big enough for some metal snips to fit in to cut out the rest.
It worked but didn't give me too much gains. Still a great cheap hold over until you can get an upgrade.