Its not so much the shafts as the hubs themselves. If you have a look on this link, scroll down and check out the hub set up. Reckon that'll go into the CEN arms? http://www.three5models.co.uk/hyper_7_pbs.htm
The only reason I ask is, I've just got another FF from ebay and I am planning on using it for the big block. Just figured may as well try the big wheels to match!