Are you 100% certain they are hub centric? there are company's out there that claim to be but they are not to the correct spec...
Also what material are you spacers made from?
Have a read of this statement from Creation motorsports...
The Hubcentric Spacers have a 57.1mm centre bore on both the internal and external face with 134mm outer diameter. They come with a set of free 10 extended M14x1.5 high quality zinc plated wheel bolts.. They are made out of a single block of 100% aluminium and are not welded. They are called Hubcentric because they sit flush on the hub. At Creations Motorsport we do not sell universal or floating spacers as they cause too much fitment issues and result in vibration. Our spacers will fit securely onto your wheel hub, the alloy wheels will then fit directly onto your wheel spacer allowing for perfectfitment and no wheel wobble at all unlike other universal spacers.
Please make sure your hub lip does not protude more then 12mm on your wheels. If unsure please ask.
I personally have the creation motorsport spacers see here.....
http://www.creationsmotorsport.com/product-detail.php?pid=140And I get no wheel wobble at all, however my cuz when he was running 18's on his car spent £90 on wheel spacers from ebay that said they where hubcentic and he had wheel wobble, he was laughing at me when he heard I got these spacers but then was scratching his head as to why I got no wheel wobble at all.
Imho it isn't always down to the spacers, it will come down to the quality of the wheels, tyres and suspension setup.
When you got your wheels balanced, did you ask if there were any buckles?
What tyres are you using? and what wheels are they?
Also is your spacers made from alloy or steel? do they weigh the exact same?
What grade bolts are you using? are they extended? you should be running M14 20mm bolts I think.